Polymer film, optically-compensatory film, process for producing the same, polarizing plate and liquid-crystal display device

ABSTRACT

A polymer film that has: a ratio R (VT/VM) of a sound velocity in a transverse direction VT to a sound velocity in a machine direction VM of from 1.05 to 1.50; and an in-plane retardation Re(λ) and a thickness-direction retardation Rth(λ) satisfying formula (I): (I) 0≦Re(630)≦10, and |Rth(630)|≦25, wherein Re(λ) represents an in-plane retardation at a wavelength of λ (nm); and Rth(λ) represents a thickness-direction retardation at a wavelength of λ (nm).

This application is a continuation of U.S. application Ser. No.11/792,678 filed on Jun. 8, 2007, now abandoned, which is a 371 nationalstage entry of PCT/JP2006/001165 filed on Jan. 19, 2006.

TECHNICAL FIELD

This invention relates to polymer film useful in liquid crystal displaydevices, an optically compensatory film using a polymer film, a processfor producing the same, optical materials such as a polarizing plate anda liquid-crystal display device.

BACKGROUND ART

Because of being excellent in toughness and flame retardancy, celluloseacylate films have been employed in photographic supports and variousoptical materials. In recent years, in particular, cellulose acylatefilms are frequently employed as optically transparent films for liquidcrystal display devices. Owing to the high optical transparency and highoptical isotropy, cellulose acylate films are favorable as opticalmaterials for devices with the use of polarization such as liquidcrystal display devices. Therefore, cellulose acylate films have beenemployed as optically compensatory film supports whereby display inlooking from an angle can be compensated (viewing angle compensation).

A polarizing plate, which is one of members constituting a liquidcrystal display device, is constructed by bonding a polarizationfilm-protecting film to at least one side of a polarization film. Ingeneral, a polarization film is obtained by dyeing a stretched polyvinylalcohol (PVA)-based film with iodine or a dichroic dye. Such apolarization film-protecting film should be excellent in opticalisotropy and the characteristics of a polarizing plate largely depend onthe optical characteristics of the polarization film-protecting film. Asthe polarization film-protecting film, therefore, cellulose acylatefilms, in particular, triacetyl cellulose films which can be bondeddirectly to PVA are employed in may cases.

Before bonding a protecting film to a polarization film, the bondingface of the protecting film is subjected to a surface-treatment such asa hydrophilicating treatment in some cases so as to enhance theadhesiveness to the polarization film. As the hydrophilicatingtreatment, use is frequently made of an alkali saponification treatmentand it has been also proposed to employ a plasma treatment, a coronatreatment and so on therefor (see, for example, JP-A-2002-328224 andJP-A-2000-356714).

In liquid crystal display devices in these days, it is more stronglyrequired to improve viewing angle characteristics. Thus, opticallytransparent films to be used as a polarization film-protecting film, anoptically compensatory film support, etc. should have improved opticalisotropy. To be optically isotropic, it is important to have a smallretardation value represented by the product of the birefringence andthickness of an optical film. To improve the display in looking from anangle, it is particularly needed to lower not only the in-planeretardation value (Re) but also the thickness direction retardationvalue (Rth). More specifically speaking, it is needed that, in the caseof evaluating the optical characteristics of an optically transparentfilm, Re measured in plane is a small value and Re shows no change eventhough the measurement angle is varied.

Although there have been cellulose acylate films having a small in-planeretardation Re, a cellulose acylate film having a small change in Redepending on angle, i.e., having a small Rth can be hardly produced.Thus, there have been proposed optically transparent films with littleangle-dependent change in retardation with the use of apolycarbonate-based film or a thermoplastic cycloolefin film as asubstitute for a cellulose acylate film (see, for example,JP-A-2001-318233 and JP-A-2002-328233; examples of commerciallyavailable products being ZEONOR (manufactured by ZEON CORPORATION) andARTON (manufactured by JSR)). In the case of using as a polarizationfilm-protecting film, however, these optically transparent films sufferfrom a problem in the bonding properties to PVA. Moreover, there stillremains another problem that the optical characteristics in the entirefilm face are uneven. To overcome these problems, it is efficacious tofurther lower the optical anisotropy.

In producing a cellulose acylate film, it has been a practice to add acompound called a plasticizer to thereby improve the film-formingperformance. Examples of the plasticizer include phosphoric acidtriesters such as triphenyl phosphate and biphenyldiphenyl phosphate andphthalic acid esters and so on (see, for example, Purasuchikku ZairyoKoza, vol. 17, Nikkan Kogyo Shinbun, Ltd., Senisokei Jushi, p. 121(1970)). It is known that some of these plasticizers have an effect oflowering the optical anisotropy of a cellulose acylate film. Forexample, specific fatty acid esters are disclosed (see, for example,JP-A-2001-247717). However, these known compounds can onlyinsufficiently lower the optical anisotropy of a cellulose acylate film.

As a method of producing a biaxial optically compensatory film to beused in liquid crystal display devices in recent years, there has beenproposed a method which comprises providing a thin layer having ahigh-molecular weight polymer as the main component on a supportingmaterial and orienting the high-molecular weight polymer by either astretching treatment, a shrinking treatment or both of them to therebygive an optical film having a desired retardation (see JP-A-2003-315541,JP-A-2001-344856, JP-A-2004-46097 and JP-A-2004-78203). In this method,the supporting material should have small Re and Rth after thestretching or shrinking treatment too. However, supporting materialsproposed hitherto have large retardation after the stretching orshrinking treatment or polarizing plates constructed by using the thusobtained optically compensatory films as protecting films suffer fromsome problems in the bonding properties or durability.

DISCLOSURE OF THE INVENTION

To solve the above-described problems, there is required a film having alow optical anisotropy after a stretching or shrinking treatment. Morespecifically speaking, it is strongly required to develop an opticallytransparent and optically isotropic film which has an in-planeretardation (Re) of almost zero, shows little angle-dependent change inthickness direction retardation (Rth) (i.e., Rth being almost zero too)and, furthermore, can be adequately bonded to PVA.

In liquid-crystal display devices of recent years, it is also requiredto improve display colors. For this purpose, it is necessary in anoptically-transparent film to be used as support of a polarizationfilm-protecting film or an optically-compensatory film not only tolessen Re and Rth in the visible region of 400 to 800 nm in wavelengthbut also to lessen changes in Re and Rth depending on wavelength, i.e.,wavelength dispersion.

As an additional problem, it is further required to provide anoptically-compensatory film or a polarizing plate with the use of such ahigh-function polymer film having improved viewing angle characteristicsand visibility at a high productivity and a low cost. More specificallyspeaking, it is proposed, for example, processes for producingoptically-compensatory films by performing a stretching treatment or ashrinking treatment by the batch type method or the roll (roll to roll)method as described in the above JP-A-2003-315541, JP-A-2001-344856,JP-A-2004-46097 and JP-A-2004-78203. From the viewpoint of productivity,continuous production to give a polarizing plate by the roll method ispreferred.

An object of the invention is to provide a polymer film which has a lowoptical anisotropy (i.e., being substantially optically isotropic), evenoptical characteristics without irregularities (preferably having asmall wavelength dispersion in the optical anisotropy) and controlledbonding properties so that it is appropriately usable in image displaydevices such as liquid-crystal display devices.

Another object of the invention is to provide an optically-compensatoryfilm using the above polymer film, a polarizing plate having excellentviewing angle characteristics and a liquid-crystal display device usingthe above polarizing plate.

Another object of the invention is to provide a process for producingthe polymer film and the optically-compensatory film as described above.

As the results of intensive studies, the inventors have found out thatthe above problems can be solved by providing a polymer film that has aratio R (VT/VM) of the sound velocity in the transverse direction VT tothe sound velocity in the machine direction VM, and an in-planeretardation Re(λ) and a thickness-direction retardation Rth(λ) eachbeing lowered as far as possible. They have further found out that theabove problems can be solved by providing a polymer film wherein theratio of the tensile modulus in the transverse direction to the tensilemodulus in the machine direction is specified and the in-planeretardation Re(λ) and the thickness-direction retardation Rth(λ) arelowered as far as possible.

In the polymer film of the invention, the ratio R (VT/VM) of the soundvelocity in the transverse direction VT to the sound velocity in themachine direction VM is from 1.05 to 1.50, preferably from 1.06 to 1.45and more preferably from 1.07 to 1.40.

It is also preferable that the polymer film of the invention has atensile modulus in the transverse direction of from 240 to 600 kgf/mm²(2.35 GPa to 5.88 GPa), preferably from 250 to 580 kgf/mm² (2.45 GPa to5.68 GPa), a tensile modulus in the machine direction of from 230 to 480kgf/mm² (2.25 GPa to 4.70 GPa), preferably from 240 to 470 kgf/mm² (2.35GPa to 4.61 GPa), and a ratio of the former tensile modulus in thetransverse direction to the latter tensile modulus in the machinedirection (former/latter) of from 1.15 to 1.80, preferably from 1.16 to1.60.

In the invention, a polymer film having low optical anisotropy (Re, Rth)has an in-plane retardation at a wavelength of 630 nm Re(630) of notmore than 10 nm (0≦Re(630)≦10) and the absolute value of athickness-direction retardation at a wavelength of 630 nm Rth(630) ofnot more than 25 nm (|Rth(630)|≦25 nm), more preferably 0≦Re(630)≦5 and|Rth(630)|≦20 nm and especially preferably 0≦Re(630)≦2 and |Rth(630)|≦15nm.

In the case of using a polymer film, the sound velocity, tensile modulusand optical anisotropy of which do not fall within the ranges asspecified above, for example, a protecting film for a polarizing plate,light leakage arises in the vertical or diagonal direction inlight-shielding with a cross Nicol polarizing plate, which results inlight leakage in the case where it is employed as a polarizingplate-protecting film to be used in a liquid crystal panel.

It has been further found out that bonding properties (pastingproperties) to another member (for example, a polarization film) can beimproved by controlling the surface energy of the polymer film.

As the results of intensive studies, the inventors have furthermorefound out that the polymer film can be prevented from coloration withthe passage of time by using a compound having an absorption in theultraviolet region of 200 to 400 nm and, moreover, the wavelengthdispersion of the polymer film can be thus regulated and the absolutevalue of the differences between Re and Rth at 400 nm and 700 nm, i.e.,|Re(400)−Re(700)| and |Rth(400)−Rth(700)|.

In the invention, it is preferable that the differences in the absoluteRe and Rth a described above are |Re(400)−Re(700)|≦10 and|Rth(400)−Rth(700)|≦35, more preferably |Re(400)−Re(700)|≦5 and|Rth(400)−Rth(700)=25 and especially preferably |Re(400)−Re(700)|≦3 and|Rth(400)−Rth(700)≦15.

It has been also confirmed that, in the case of using a celluloseacylate film as the polymer film, such a compound is highly compatiblewith cellulose acylate in the course of producing the cellulose acylatefilm so that there arises no clouding and the obtained film has asufficient physical strength.

As the results of intensive studies, the inventors have furthermorefound out that the above problems can be solved even by using acellulose acylate film having a high degree of acyl substitution as thepolymer film.

The inventors have furthermore found out that an optically-compensatoryfilm having excellent viewing angle characteristics can be provided byforming an optically-anisotropic layer on the polymer film of theinvention. It has been also found out that the polymer film and theoptically-compensatory film of the invention are useful in polarizingplates and liquid-crystal display devices.

Accordingly, the present invention is as follows.

(1) A polymer film that has: a ratio R (VT/VM) of a sound velocity in atransverse direction VT to a sound velocity in a machine direction VM offrom 1.05 to 1.50; and an in-plane retardation Re(λ) and athickness-direction retardation Rth(λ) satisfying formula (I):0≦Re(630)≦10, and |Rth(630)|≦25  (I)

-   -   wherein Re(λ) represents an in-plane retardation at a wavelength        of λ (nm); and Rth(λ) represents a thickness-direction        retardation at a wavelength of λ (nm).

(2) A polymer film that has: a tensile modulus in a transverse directionof from 240 to 600 kgf/mm² (2.35 GPa to 5.88 GPa); a tensile modulus inthe machine direction of from 230 to 480 kgf/mm² (2.25 GPa to 4.70 GPa);a ratio of a tensile modulus in a transverse direction to a tensilemodulus in a machine direction of from 1.15 to 1.80; and an in-planeretardation Re(λ) and a thickness-direction retardation Rth(λ)satisfying formula (I):0≦Re(630)≦10, and |Rth(630)|≦25;  (I)

-   -   wherein Re(λ) represents an in-plane retardation at a wavelength        of λ (nm); and    -   Rth(λ) represents a thickness-direction retardation at a        wavelength of λ (nm).

(3) The polymer film as described in (1) or (2) above, which has atleast one surface having a surface energy of 50 mN/m or more but notmore than 80 mN/m.

(4) The polymer film as described in (3) above, which has at least onesurface-treated surface,

wherein the at least one surface-treated surface has a surface energy of30 mN/m or more but not more than 50 mN/m before a surface treatment,and has a surface energy of 50 mN/m or more but not more than 80 mN/mafter a surface treatment.

(5) The polymer film as described in any of (1) to (4) above, which hasan in-plane retardation Re(λ) and a thickness-direction retardationRth(λ) satisfying formula (II):|Re(400)−Re(700)|≦10, and |Rth(400)−Rth(700)|≦35;  (II)

-   -   wherein Re(λ) represents an in-plane retardation at a wavelength        of λ (nm); and    -   Rth(λ) represents a thickness-direction retardation at a        wavelength of λ (nm).

(6) The polymer film as described in any of (1) to (5) above, which is apolymer film comprising at least a cellulose acylate and a compoundhaving a molecular weight of not more than 3000.

(7) The polymer film as described in (6) above,

wherein an acyl substituent in the cellulose acylate is substantially anacetyl group alone, a total degree of substitution thereof is from 2.80to 2.99, and a mean degree of polymerization of the cellulose acylate isfrom 180 to 550.

(8) The polymer film as described in (6) above,

wherein an acylate group in the cellulose acylate comprises at least oneof acetate, propionate and butylate, and a total degree of substitutionthereof is from 2.50 to 3.00.

(9) The polymer film as described in any of (1) to (8) above, which hasa photoelasticity coefficient of not more than 25×10⁻¹³ cm²/dne(2.5×10⁻¹³ N/m²).

(10) An optically-compensatory film comprising:

a polymer film as described in any of (1) to (9) above; and

an optically-anisotropic layer formed on the polymer film,

wherein the optically-anisotropic layer satisfies formulae: Re(630)=0 to200 (nm), and |Rth(630)|=0 to 400 (nm).

(11) The optically-compensatory film as described in (10) above,

wherein the optically-anisotropic layer comprises a polymer film.

(12) The optically-compensatory film as described in (11) above that isobtained by a method comprising:

spreading a polymer having been dissolved in a solvent and thusliquefied on a polymer film as described in any of (1) to (9) above, soas to obtain a laminate; and

subjecting the thus obtained laminate to a stretching treatment, ashrinking treatment or both of them to thereby orient polymer moleculesin the plane.

(13) The optically-compensatory film as described in (11) or (12) above,

wherein the polymer film comprises at least one polymer selected fromthe group consisting of polyamide, polyimide, polyester,polyetherketone, polyaryl-ether ketone, polyamidimde and polyesterimide.

(14) A process for producing a polymer film as described in any of (1)to (9) above, which comprises stretching a film in a transversedirection.

(15) A process for producing a polymer film as described in any of (1)to (9) above, which comprises shrinking a film in a machine direction.

(16) A process for producing an optically-compensatory film as describedin any of (10) to (13) above, which comprises:

spreading a polymer having been dissolved in a solvent and thusliquefied on a polymer film, so as to obtain a laminate; and

stretching the thus obtained laminate in a transverse direction.

(17) A process for producing an optically-compensatory film as describedin any of (10) to (13) above, which comprises:

spreading a polymer having been dissolved in a solvent and thusliquefied on a polymer film, so as to obtain a laminate; and

shrinking the thus obtained laminate in a machine direction.

(18) A process for producing the optically-compensatory film asdescribed in any of (10) to (13) above, which comprises:

layering a polymer having been dissolved in a solvent and thus liquefiedon a polymer film by a co-casting method, so as to obtain a laminate;and

stretching the thus obtained laminate in a transverse direction.

(19) A polarizing plate comprising at least one of a polymer film asdescribed in any of (1) to (9) above and an optically-compensatory filmas described in any of (10) to (13) above as a protecting film for apolarization film.

(20) The polarizing plate as described in (19) above, which has at leastone layer selected from the group consisting of a hard coat layer, anantiglare layer and an antireflection layer provided on a surface of thepolarizing plate.

(21) A liquid-crystal display device, which comprises at least one of apolymer film as described in any of (1) to (9) above, anoptically-compensatory film as described in any of (10) to (13) aboveand a polarizing plate as described in (19) or (20) above.

(22) The liquid-crystal display device as described in (21) above, whichis a VA or IPS liquid-crystal display device.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, the polymer film of the invention will be illustrated in greaterdetail.

[Material of Polymer Film]

It is preferable that the polymer film of the invention is made of apolymer material being excellent in optical performance, transparency,mechanical strength, heat stability, moisture-blocking properties,isotropy and so on. Any material may be used so long as Re and Rth asdescribed above satisfy the above formula (I). For example, use can bemade of polycarbonate-based polymers, polyester-based polymers such aspolyethylene terephthalate and polyethylene naphthalate, acrylicpolymers such as polymethyl methacrylate, styrene-based polymers such aspolystyrene and acrylonitrile-styrene copolymer (AS resin) and so on.Further examples include polyolefins such as polyethylene andpolypropylene, olefin-based polymers such as ethylene-propylenecopolymer, vinyl chloride-based polymers, amide-based polymers such asnylon and aromatic polyamide, imide-based polymers, sulfone-basedpolymers, polyether sulfone-based polymers, polyether ether ketone-basedpolymers, polyphenylene sulfide-based polymers, vinylidenechloride-based polymers, vinyl alcohol-based polymers, vinylbutyral-based polymers, arylate-based polymers, polyoxymethylene-basedpolymers, epoxy-based polymers and polymers prepared by mixing theabove-described polymers. The polymer of the invention may be formed asa hardening layer made of an ultraviolet-hardening or heat-hardeningresin.

As a material for forming the polymer film of the invention, it ispreferable to use a thermoplastic norbornene-based resin. As examples ofthe thermoplastic norbornene-based resin, ZEONOR (manufactured by ZEONCORPORATION) and ARTON (manufactured by JSR)) can be cited.

As a material for forming the polymer film of the invention, it is alsopreferable to use a cellulose-based polymer (hereinafter referred to ascellulose acylate) typified by triacetyl cellulose which has been usedas transparent protecting films in polarizing plates. Next, celluloseacylate film will be mainly illustrated as an example of the polymerfilm of the invention. However, it is obvious that technical mattersthereof are also applicable to other polymer films.

[Starting Cotton Material for Synthesizing Cellulose Acylate]

Examples of the starting cellulose to be used for synthesizing thecellulose acylate in the invention include cotton linter and wood pulp(hardwood pulp and softwood pulp). Use can be made of cellulose acylateobtained from any cellulose material and a mixture is also usable insome cases. These starting cotton materials are described in detail in,for example, Purasuchikku Zairyo Kozo (17), Senisokei Jushi (Marusawaand Uda, The Nikkan Kogyo Shinbun, Ltd., 1970) and Japan Institute ofInvention and Innovation Journal of Technical Disclosure No. 2001-1745,p. 7 to 8, though the material of the cellulose acylate film of theinvention is not particularly restricted thereto.

[Degree of Substitution in Cellulose Acylate]

Now, the cellulose acylate which is produced starting with the cellulosematerial as described above will be illustrated. In the celluloseacylate in the invention, hydroxyl groups in cellulose have beenacylated. As the substituents, use may be made of acetyl groups havingfrom 2 to 22 carbon atoms. In the cellulose acylate to be used in theinvention, the degree of substitution of hydroxyl groups in thecellulose is not particularly restricted. The substitution degree can bedetermined by measuring the degree of binding of acetic acid and/orfatty acids having from 3 to 22 carbon atoms substituting hydroxylgroups in cellulose and calculating. The measurement can be carried outin accordance with ASTM D-817-91.

As described above, the degree of substitution of hydroxyl groups in thecellulose is not particularly restricted in the cellulose acylate to beused in the invention. It is preferable that the degree of substitutionof hydroxyl group by acyl group is from 2.50 to 3.00, more preferablyfrom 2.75 to 3.00 and more preferably from 2.85 to 3.00.

Among the acetic acid and/or fatty acids having from 3 to 22 carbonatoms substituting hydroxyl groups in cellulose, the acyl group havingfrom 2 to 22 carbon atoms may be an aliphatic group or an aromatic groupwithout restriction. Either a single group or a mixture of two or moregroups may be used. Use may be made of, for example, alkylcarbonylesters, alkenylcarbonyl esters, aromatic carbonyl esters and aromaticalkylcarbonyl esters of cellulose each optionally having additionalsubstituents. Preferable examples of the acyl group include acetyl,propionyl, butanoyl, heptanoyl, hexanoyl, octanoyl, decanoyl,dodecanoyl, tridecanoyl, tetradecanoyl, hexadecanoyl, octadecanoyl,iso-butanoyl, t-butanoyl, cyclohexanecarbonyl, oleoyl, benzoyl,naphthylcarbonyl and cinnamoyl groups. Among them, acetyl, propionyl,butanoyl, dodecanoyl, octadecanoyl, t-butanoyl, oleoyl, benzoyl,naphthylcarbonyl cinnamoyl groups are preferable, and acetyl, propionyland butanoyl groups are more preferable.

As the results of intensive studies, the inventors have found out thatthe optical isotropy of a cellulose acylate film can be lowered in thecase where acylate groups substituting hydroxyl groups in the celluloseacylate comprise substantially at least two of acetyl, propionyl andbutanoyl groups and the degree of substitution thereof is from 2.50 to3.00. The degree of acyl substitution preferably is from 2.60 to 3.00,more preferably from 2.65 to 3.00. In the case where the acyl groupssubstituting hydroxyl groups in the cellulose are substantially acetylgroup alone, the optical anisotropy of the film can be lowered. From theviewpoints of the compatibility with an additive and the solubility inan organic solvent employed, it is more preferable that the degree ofsubstitution is from 2.80 to 2.99, more preferably from 2.85 to 2.95.

[Degree of Polymerization of Cellulose Acylate]

The degree of polymerization (expressed in viscosity-average degree ofpolymerization) of the cellulose acylate preferably used in theinvention ranges from 180 to 700. In cellulose acetate, the degree ofpolymerization preferably ranges from 180 to 550, more preferably from180 to 400 and especially preferably from 180 to 350. In the case wherethe degree of polymerization is too high, a dope solution of thecellulose acylate has a high viscosity and, in its turn, a film can behardly formed by casting. An average degree of polymerization can bemeasured by the limiting viscosity method reported by Uda et al. (KazuoUda & Hideo Saito, SEN-I GAKKAISHI, Vol. 18, No. 1, p. 105-120, 1962).This method is reported in greater detail in JP-A-9-95538.

The molecular weight distribution of the cellulose acylate preferablyused in the invention is evaluated by gel permeation chromatography. Asmaller polydispersity index Mw/Mn (Mw: mass-average molecular weight,Mn: number-average molecular weight) and a narrower molecular weightdistribution are preferred. More specifically speaking, Mw/Mn preferablyranges from 1.0 to 3.0, more preferably from 1.0 to 2.0 and mostdesirably from 1.0 to 1.6.

When low-molecular weight components are removed, the average molecularweight (degree of polymerization) is elevated but the viscosity becomeslower than common cellulose acylates, thereby becoming useful. Celluloseacylate containing less low-molecular weight components can be obtainedby removing the low-molecular weight components from cellulose acylatesynthesized by a conventional method. The low-molecular weightcomponents can be removed by washing cellulose acylate with anappropriate organic solvent. In the case of producing cellulose acylatecontaining less low-molecular weight components, it is preferable tocontrol the amount of the sulfuric acid catalyst in the acetylation to0.5 to 25 parts by mass per 100 parts by mass of cellulose acylate. (Inthis specification, parts by mass and % by mass are equal to parts byweight and % by weight, respectively.) By controlling the amount of thesulfuric acid catalyst within the range as described above, it ispossible to synthesize cellulose acylate favorable from the viewpoint ofmolecular weight distribution (i.e., having an even molecular weightdistribution). In the production of cellulose acylate according to theinvention, use is made of cellulose acylate having a water content ratioof preferably 2% by mass or less, more preferably 1% by mass or less andespecially preferably 0.7% by mass or less. In general, celluloseacylate contains water and it is known that the water content ratiothereof ranges from 2.5 to 5% by mass. To regulate to this water contentratio of cellulose acylate in the invention, it is required to dry thecellulose acylate. The drying method is not particularly restricted, solong as the desired water content ratio can be established thereby. Toobtain cellulose acylate usable in the invention, use can be made of thesynthesis method described in detail in Japan Institute of Invention andInnovation Journal of Technical Disclosure No. 2001-1745 (2001.03.15,Japan Institute of Invention and Innovation), p. 7 to 12.

As the cellulose acylate to be used in the invention, use can be made ofeither a single cellulose acylate or a mixture of two or more celluloseacylates so long as these cellulose acylates fulfill the requirements insubstituent, degree of substitution, degree of polymerization, molecularweight distribution and so on as described above.

[Additives to Cellulose Acylate]

To a cellulose acylate of the invention, it is possible to add variousadditives (for example, a compound capable of lowering opticalanisotropy (also called optical anisotropy-lowering agent), a wavelengthdispersion regulator, fine particles, a plasticizer, a UV-blockingagent, an antidegradant, a releasing agent, an opticalcharacteristic-controlling agent, etc.). Now, these additives will beillustrated. These additives may be added in the step of preparing thedope (the step of preparing a cellulose acylate solution).Alternatively, a step of adding the additives may be provided in thefinal step of preparing the dope.

By controlling the amounts of these additives, it is possible to satisfythe requirement of the present invention:0≦Re(630)≦10, and |Rth(630)|≦25;  (I)and a preferable condition thereof:|Re(400)−Re(700)|≦10, and |Rth(400)−Rth(700)|≦35.  (II)

It is preferable that (I) 0≦Re(630)≦5 and |Rth(630)|≦20, more preferably0≦Re(630)≦2 and |Rth(630)|≦15. It is also preferable that (II)|Re(400)−Re(700)|≦5 and |Rth(400)−Rth(700)|≦25, more preferably|Re(400)−Re(700)|≦3 and |Rth(400)-Rth(700)|≦15.

In the formulae, Re(λ) represents an in-plane retardation at awavelength of λ (nm); and Rth(λ) represents a thickness-directionretardation at a wavelength of λ (nm).

It is preferable that the cellulose acylate film of the inventioncontains at least one compound represented lowering the opticalanisotropy (in particular, the thickness-direction retardation Rth)within such a range as satisfying the requirements as specified by thefollowing formulae (II) and (iii):(Rth(A)−Rth(0))/A≦−1.0  (ii)0.01≦A≦30;  (iii)wherein Rth(A) is Rth (nm) of a film containing A % of the compoundcapable of lowering Rth; Rth(0) is Rth (nm) of a film containing nocompound capable of lowering Rth; and A is the mass (%) of the compoundreferring the mass of the polymer employed as the film material as to100.

Concerning the above formulae (II) and (iii), it is preferable that:(Rth(A)−Rth(0))/A≦−2.0  (ii)0.05≦A≦25;  (iii)still preferably:(Rth(A)−Rth(0))/A≦−3.0  (ii)0.01≦A≦20;  (iii)[Structural Characteristic of Compound Capable of Lowering OpticalAnisotropy of Cellulose Acylate Film]

Now, the compound capable of lowering optical anisotropy of a celluloseacylate film will be illustrated. As the results of intensive studies,the inventors sufficiently lowered the optical anisotropy by using acompound inhibiting the orientation of cellulose acylate in a film inplane and in the film thickness direction, thereby reducing Re and Rthclose to zero. For this purpose, it is advantageous to employ a compoundcapable of lowering optical anisotropy which is sufficiently compatiblewith cellulose acylate and has neither a rod-like structure nor a planarstructure by itself. In the case of having a plural number of planarfunctional groups such as aromatic groups, more specifically speaking, anonplanar structure having these functional groups not on a single planeis advantageous.

(LogP Value)

To produce the cellulose acylate film of the invention, it is preferableto employ, from among the compounds which prevent cellulose acylate inthe film from orientation in-plane and in the film thickness directionto thereby lower optical anisotropy, a compound having an octanol-waterpartition coefficient (log P value) of from 0 to 7. A compound having alog P value exceeding 7 has a poor compatibility with cellulose acylateand thus frequently results in clouding or blooming of the film. Acompound having a log P value less than 0 has highly hydrophilic naturewhich sometimes worsens the water resistance of the cellulose acylatefilm. It is still preferable that the log P value ranges from 1 to 6,especially preferably from 1.5 to 5.

The octanol-water partition coefficient (log P value) can be measured bythe flask shaking method in accordance with JIS Z7260-107 (2000). It isalso possible to estimate the octanol-water partition coefficient (log Pvalue) by using not practical measurement but a computational orempirical method. As the computational method, use may be preferablymade of Crippen's fragmentation method (J. Chem. Inf. Comput. Sci., 27,21 (1987)), Viswanadhan's fragmentation method (J. Chem. Inf. Comput.Sci., 29, 163 (1989)), Broto's fragmentation method (Eur. J. Med.Chem.-Chim. Theor., 19, 71 (1984)) and so on. It is still preferable toemploy Crippen's fragmentation method (J. Chem. Inf. Comput. Sci., 27,21 (1987)). In the case where the log P value of a compound determinedby the measurement method differs from its calculated value, it isfavorable to judge whether or not the compound falls within the desiredrange with the use of Crippen's fragmentation method. The log P valuesgiven in the present specification are determined by Crippen'sfragmentation method (J. Chem. Inf. Comput. Sci., 27, 21 (1987)).

[Physical Properties of Compound Capable of Lowering Optical Anisotropy]

The compound having the ability to lower the optical anisotropy of filmmay have or may not have an aromatic group. Preferably, the compoundhaving the ability to lower the optical anisotropy of film has amolecular weight of from 150 to 3000, more preferably from 170 to 2000,further more preferably from 200 to 1000. So far as having a molecularweight that falls within the range, the compound may have a specificmonomer structure or may have an oligomer structure or a polymerstructure with a plurality of such monomer units bonding to each other.

Preferably, the compound having the ability to lower the opticalanisotropy of film is liquid at 25° C., or is a solid having a meltingpoint of from 25 to 250° C., more preferably it is liquid at 25° C., oris a solid having a melting point of from 25 to 200° C. Preferably, thecompound having the ability to lower the optical anisotropy of film doesnot evaporate away in the dope-casting and drying process of celluloseacylate film formation.

The amount of the compound capable of lowering optical anisotropy to beadded to the film-forming dope in the invention is preferably from 0.01to 30% by mass of cellulose acylate, more preferably from 1 to 25% bymass, even more preferably from 5 to 20% by mass.

One or more different types of compounds capable of lowering opticalanisotropy may be used herein either singly or as combined in anydesired ratio.

The time when the compound capable of lowering optical anisotropy isadded to the film-forming dope may be any one during the process of dopepreparation, and the compound may be added to the done in the final stepof the dope preparation.

Regarding the content of the compound capable of lowering opticalanisotropy in the cellulose acylate film in the invention, the meancontent of the compound in the part of up to 10% of the overallthickness of the film from at least one surface side of the film is from80 to 99% of the mean content of the compound in the center part of thefilm. The amount of the compound in the film in the invention may bedetermined by measuring the amount thereof in the surface part of thefilm and that in the center part thereof through IR absorptionspectrometry as in JP-A 8-57879.

As specific examples of the compound capable of lowering opticalanisotropy of the cellulose acylate film to be preferably used in theinvention, a compound represented by any one of the following formulae(13), (18) and (19) may be cited, though the invention is not restrictedthereto.

In the formula (13), R¹ represents an alkyl group or an aryl group; andR² and R³ each independently represents a hydrogen atom, an alkyl groupor an aryl group, provided that the sum of the carbon atoms in R¹, R²and R³ is 10 or more.

In the formula (18), R¹ represents an alkyl group or an aryl group; andR² and R³ each independently represents a hydrogen atom, an alkyl groupor an aryl group.

In the formula (19), R⁴, R⁵ and R⁶ each independently represents analkyl group or an aryl group.

Now, the compounds of the formulae (13) and (14) will be described.

In the above formula (13), R¹ represents an alkyl group or an arylgroup. R² and R³ independently represent each a hydrogen atom, an alkylgroup or an aryl group. It is especially preferable that the sum of thecarbon atoms in R¹, R² and R³ is 10 or more. R¹, R² and R³ may besubstituted and preferable examples of the substituent include afluorine atom, alkyl groups, aryl groups, alkoxy groups, sulfone groupand sulfonamido group. Among all, alkyl groups, aryl groups, alkoxygroups, sulfone group and sulfonamido group are particularly preferable.The alkyl group may be either chain type, branched or cyclic. It ispreferable that the alkyl group has from 1 to 25 carbon atoms, morepreferably from 6 to 25 carbon atoms and especially preferably from 6 to20 carbon atoms (for example, methyl, ethyl, propyl, isopropyl, butyl,isobutyl, t-butyl, amyl, isoamyl, t-amyl, hexyl, cyclohexyl, heptyl,octyl, bicyclooctyl, nonyl, adamantyl, decyl, t-octyl, undecyl, dodecyl,tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl,nonadecyl and didecyl). The aryl group preferably has from 6 to 30carbon atoms, more preferably from 6 to 24 carbon atoms (for example,phenyl, biphenyl, terphenyl, naphthyl, binaphthyl and triphenylphenyl).Next, preferable examples of the compounds represented by the formula(13) will be presented, though the invention is not restricted to thesespecific examples.

Next, the compounds represented by the formula (18) or the formula (19)will be described, though the invention is not restricted to thesespecific examples. In the compounds represented by the formula (18) orthe formula (19), specific examples of alkyl and aryl groups are thesame as in the formula (13).

In the above formulae, Pr^(i) represents an isopropyl group.

[Wavelength Dispersion Regulator]

Next, a compound lessening wavelength dispersion of the celluloseacylate film (hereinafter referred to as a wavelength dispersionregulator) will be illustrated. It is preferable that the celluloseacylate film of the invention contains at least one compound capable oflowering the wavelength dispersion of Rth represented by the followingformula (iii) ΔRth=|Rth₍₄₀₀₎−Rth₍₇₀₀₎| within a range of satisfying thefollowing formulae (iv) and (v):ΔRth=|Rth ₍₄₀₀₎ −Rth _(A(700))|(iii)(ΔRth(B)−ΔRth(0))/B≦−2.0;  (iv)0.01≦B≦30:  (v)wherein ΔRth(B) is ΔRth (nm) of a film containing B % of the compoundcapable of lowering wavelength dispersion of Rth; ΔRth(0) is ΔRth (nm)of a film containing no compound capable of lowering wavelengthdispersion of Rth; and B is the mass (%) of the compound referring themass of the cellulose acylate as to 100.

Concerning the above formulae (iv) and (v), it is preferable that:(ΔRth(B)−ΔRth(0)/B)−3.0  (iv)0.05≦B≦25:  (v)still preferably:(ΔRth(B)−ΔRth(0)/B)−4.0  (iv)0.1≦B≦20.  (v)

As the wavelength dispersion regulator as described above, it ispreferable to use a compound having an absorption in the ultravioletregion of 200 to 400 nm and being capable of lowering both of|Re(400)−Re(700)| and |Rth(400)−Rth(700)|. It is advantageous to usesuch a compound in an amount of from 0.01 to 30% by mass based on thesolid content of cellulose acylate.

Regarding the wavelength-dependent distribution thereof, the values ofRe and Rth of cellulose acylate film are generally larger in a shortwavelength range than in a long wavelength range. Therefore, it isdesired that the small values of Re and Rth in a short wavelength rangeare increased to thereby reduce the wavelength-dependent Re and Rthdistribution. On the other hand, the wavelength-dependent characteristicdistribution of compounds having an absorption in a UV range of from 200to 400 nm is such that the absorbance of the compound is larger in along wavelength range than in a short wavelength range. When a compoundof the type is isotropically inside cellulose acylate film, then thebirefringence and therefore the wavelength-dependent Re and Rthdistribution of the compound may be larger in the short wavelength rangelike the wavelength-dependent absorbance distribution thereof.

Accordingly, when a compound having an absorption in a UV range of from200 to 400 nm and probably having a larger wavelength-dependent Re andRth distribution in a short wavelength range, such as that mentionedabove, is used in a cellulose acylate film, then thewavelength-dependent Re and Rth distribution the film could becontrolled. For this, the compound having the ability to control thewavelength-dependent anisotropy distribution of cellulose acylate filmmust be satisfactorily and uniformly miscible with cellulose acylate.Preferably, the compound of the type has a UV absorption range of from200 to 400 nm, more preferably from 220 to 395 nm, even more preferably240 to 390 nm.

In recent liquid-crystal display devices for televisions, notebook-sizepersonal computers and mobile display terminals, the optical members arerequired to have a high transmittance in order that the display devicescan have a high brightness at a smaller power. In this point, when acompound having an absorption in a UV region of from 200 to 400 nm andhaving the ability to reduce |Re(400)−Re(700)| and |Rth(400)−Rth(700)|of cellulose acylate film is added to the film, it is desired that thefilm with the compound added thereto could have a high spectraltransmittance. Preferably, the cellulose acylate film in the inventionhas a spectral transmittance at a wavelength of 380 nm of from 45% to95%, and has a spectral transmittance at a wavelength of 350 nm of atmost 10%.

From the viewpoint of the vaporization thereof, it is desirable that thewavelength-dependent anisotropy distribution improver preferred for usein the invention such as that mentioned hereinabove has a molecularweight of from 250 to 1000, more preferably from 260 to 800, even morepreferably from 270 to 800, still more preferably from 300 to 800.Having a molecular weight that falls within the range, the improver mayhave a specific monomer structure or may have an oligomer structure or apolymer structure that comprises plural monomer units bonding to eachother.

It is desirable that the wavelength-dependent anisotropy distributionimprover does not evaporate away during the process of dope-casting anddrying in cellulose acylate film formation.

(Amount of Compound to be Added)

It is desirable that the amount of the above-mentionedwavelength-dependent anisotropy distribution improver preferable for usein the invention is from 0.01 to 30% by mass of cellulose acylate, morepreferably from 0.1 to 20% by mass, even more preferably from 0.2 to 10%by mass.

(Method of Addition of Compound)

One or more different types of such wavelength-dependent anisotropydistribution improvers may be used herein either singly or as combined.

Regarding its addition, the wavelength-dependent anisotropy distributionimprover may be added to the film-forming dope in any stage of dopepreparation or in the last step of dope preparation.

Specific examples of the wavelength-dependent anisotropy distributionimprover preferred for use in the invention are benzotriazole compounds,benzophenone compounds, cyano group-containing compounds,oxybenzophenone compounds, salicylate compounds and nickel complex saltcompounds, to which, however, the invention should not be limited.Hereafter, preferred compounds are exemplified.

Preferred examples of benzotriazole compounds for use as thewavelength-dependent anisotropy distribution improver in the inventionare those of the following formula (101):Q¹-Q²-OH

wherein Q¹ represents a nitrogen-containing aromatic hetero ring; and Q²represents an aromatic ring.

Q¹ is a nitrogen-containing aromatic hetero ring, preferably a 5- to7-membered nitrogen-containing aromatic hetero ring, more preferably a5- or 6-membered nitrogen-containing aromatic hetero ring, including,for example, imidazole, pyrazole, triazole, tetrazole, thiazole,oxazole, selenazole, benzotriazole, benzothiazole, benzoxazole,benzoselenazole, thiadiazole, oxadiazole, naphthothiazole,naphthoxazole, azabenzimidazole, purine, pyridine, pyrazine, pyrimidine,pyridazine, triazine, triazaindene, tetrazaindene. More preferably, Q¹is a 5-membered nitrogen-containing aromatic hetero ring, concretelyincluding imidazole, pyrazole, triazole, tetrazole, thiazole, oxazole,benzotriazole, benzothiazole, benzoxazole, thiadiazole, oxadiazole, andis especially preferably benzotriazole.

The nitrogen-containing aromatic hetero ring for Q¹ is may have asubstituent. For the substituent, the substituents T mentioned below areapplicable. Plural substituents, if any, may be condensed to form acondensed ring.

The aromatic ring for Q² may be an aromatic hydrocarbon ring or anaromatic hetero ring. This may be a single ring or may form a condensedring with any other ring.

The aromatic hydrocarbon ring is preferably a monocyclic or bicyclicaromatic hydrocarbon ring having from 6 to 30 carbon atoms (e.g.,benzene ring, naphthalene ring), more preferably an aromatic hydrocarbonring having from 6 to 20 carbon atoms, even more preferably from 6 to 12carbon atoms. Still more preferably, it is a benzene ring.

The aromatic hetero-ring is preferably one that contains a nitrogen atomor a sulfur atom. Examples of the hetero-ring are thiophene, imidazole,pyrazole, pyridine, pyrazine, pyridazine, triazole, triazine, indole,indazole, purine, thiazoline, thiazole, thiadiazole, oxazoline, oxazole,oxadiazole, quinoline, isoquinoline, phthalazine, naphthyridine,quinoxaline, quinazoline, cinnoline, pteridine, acridine,phenanthroline, phenazine, tetrazole, benzimidazole, benzoxazole,benzothiazole, benzotriazole, tetrazaindene. The aromatic hetero-ring ispreferably pyridine, triazine or quinoline.

The aromatic ring for Q² is preferably an aromatic hydrocarbon ring,more preferably a naphthalene ring or a benzene ring, even morepreferably a benzene ring. Q² may have a substituent. For thesubstituent, preferred are the substituents T mentioned below.

The substituents T include, for example, an alkyl group (preferablyhaving from 1 to 20 carbon atoms, more preferably from 1 to 12 carbonatoms, even more preferably from 1 to 8 carbon atoms, e.g., methyl,ethyl, iso-propyl, tert-butyl, n-octyl, n-decyl, n-hexadecyl,cyclopropyl, cyclopentyl, cyclohexyl), an alkenyl group (preferablyhaving from 2 to 20 carbon atoms, more preferably from 2 to 12 carbonatoms, even more preferably from 2 to 8 carbon atoms, e.g., vinyl,allyl, 2-butenyl, 3-pentenyl), an alkynyl group (preferably having from2 to 20 carbon atoms, more preferably from 2 to 12 carbon atoms, evenmore preferably from 2 to 8 carbon atoms, e.g., propargyl, 3-pentynyl),an aryl group (preferably having from 6 to 30 carbon atoms, morepreferably from 6 to 20 carbon atoms, even more preferably from 6 to 12carbon atoms, e.g., phenyl, p-methylphenyl, naphthyl), a substituted orunsubstituted amino group (preferably having from 0 to 20 carbon atoms,more preferably from 0 to 10 carbon atoms, even more preferably from 0to 6 carbon atoms, e.g., amino, methylamino, dimethylamino,diethylamino, dibenzylamino), an alkoxy group (preferably having from 1to 20 carbon atoms, more preferably from 1 to 12 carbon atoms, even morepreferably from 1 to 8 carbon atoms, e.g., methoxy, ethoxy, butoxy), anaryloxy group (preferably having from 6 to 20 carbon atoms, morepreferably from 6 to 16 carbon atoms, even more preferably from 6 to 12carbon atoms, e.g., phenyloxy, 2-naphthyloxy), an acyl group (preferablyhaving from 1 to 20 carbon atoms, more preferably from 1 to 16 carbonatoms, even more preferably from 1 to 12 carbon atoms, e.g., acetyl,benzoyl, formyl, pivaloyl), an alkoxycarbonyl group (preferably havingfrom 2 to 20 carbon atoms, more preferably from 2 to 16 carbon atoms,even more preferably from 2 to 12 carbon atoms, e.g., methoxycarbonyl,ethoxycarbonyl), an aryloxycarbonyl group (preferably having from 7 to20 carbon atoms, more preferably from 7 to 16 carbon atoms, even morepreferably from 7 to 10 carbon atoms, e.g., phenyloxycarbonyl), anacyloxy group (preferably having from 2 to 20 carbon atoms, morepreferably from 2 to 16 carbon atoms, even more preferably from 2 to 10carbon atoms, e.g., acetoxy, benzoyloxy), an acylamino group (preferablyhaving from 2 to 20 carbon atoms, more preferably from 2 to 16 carbonatoms, even more preferably from 2 to 10 carbon atoms, e.g.,acetylamino, benzoylamino), an alkoxycarbonylamino group (preferablyhaving from 2 to 20 carbon atoms, more preferably from 2 to 16 carbonatoms, even more preferably from 2 to 12 carbon atoms, e.g.,methoxycarbonylamino), an aryloxycarbonylamino group (preferably havingfrom 7 to 20 carbon atoms, more preferably from 7 to 16 carbon atoms,even more preferably from 7 to 12 carbon atoms, e.g.,phenyloxycarbonylamino), a sulfonylamino group (preferably having from 1to 20 carbon atoms, more preferably from 1 to 16 carbon atoms, even morepreferably from 1 to 12 carbon atoms, e.g., methanesulfonylamino,benzenesulfonylamino), a sulfamoyl group (preferably having from 0 to 20carbon atoms, more preferably from 0 to 16 carbon atoms, even morepreferably from 0 to 12 carbon atoms, e.g., sulfamoyl, methylsulfamoyl,dimethylsulfamoyl, phenylsulfamoyl), a carbamoyl group (preferablyhaving from 1 to 20 carbon atoms, more preferably from 1 to 16 carbonatoms, even more preferably from 1 to 12 carbon atoms, e.g., carbamoyl,methylcarbamoyl, diethylcarbamoyl, phenylcarbamoyl), an alkylthio group(preferably having from 1 to 20 carbon atoms, more preferably from 1 to16 carbon atoms, even more preferably from 1 to 12 carbon atoms, e.g.,methylthio, ethylthio), an arylthio group (preferably having from 6 to20 carbon atoms, more preferably from 6 to 16 carbon atoms, even morepreferably from 6 to 12 carbon atoms, e.g., phenylthio), a sulfonylgroup (preferably having from 1 to 20 carbon atoms, more preferably from1 to 16 carbon atoms, even more preferably from 1 to 12 carbon atoms,e.g., mesyl, tosyl), a sulfinyl group (preferably having from 1 to 20carbon atoms, more preferably from 1 to 16 carbon atoms, even morepreferably from 1 to 12 carbon atoms, e.g., methanesulfinyl,benzenesulfinyl), an ureido group preferably having from 1 to 20 carbonatoms, more preferably from 1 to 16 carbon atoms, even more preferablyfrom 1 to 12 carbon atoms, e.g., ureido, methylureido, phenylureido), aphosphoramido group (preferably having from 1 to 20 carbon atoms, morepreferably from 1 to 16 carbon atoms, even more preferably from 1 to 12carbon atoms, e.g., diethylphosphoramido, phenylphosphoramido), ahydroxyl group, a mercapto group, a halogen atom (e.g., fluorine atom,chlorine atom, bromine atom, iodine atom), a cyano group, a sulfo group,a carboxyl group, a nitro group, a hydroxamic acid group, a sulfinogroup, a hydrazino group, an imino group, a heterocyclic group(preferably having from 1 to 30 carbon atoms, more preferably from 1 to12 carbon atoms, in which the hetero atom is any of nitrogen atom,oxygen atom or sulfur atom., e.g., imidazolyl, pyridyl, quinolyl, furyl,piperidyl, morpholino, benzoxazolyl, benzimidazolyl, benzothiazolyl), asilyl group (preferably having from 3 to 40 carbon atoms, morepreferably from 3 to 30 carbon atoms, even more preferably from 3 to 24carbon atoms, e.g., trimethylsilyl, triphenylsilyl). These substituentsmay be further substituted. Two or more substituents, if any, may be thesame or different. If possible, they may bond to each other to form aring.

Of the compounds of formula (101), preferred are those of the followingformula (101-A):

wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁷ and R⁸ each independently representsa hydrogen atom or a substituent.

R¹, R², R³, R⁴, R⁵, R⁶, R⁷ and R⁸ each independently represents ahydrogen atom or a substituent. For the substituent, referred to are thesubstituents T mentioned above. These substituents may have any othersubstituent. The substituents may be condensed to form a condensedcyclic structure.

R¹ and R³ are preferably a hydrogen atom, an alkyl group, an alkenylgroup, an alkynyl group, an aryl group, a substituted or unsubstitutedamino group, an alkoxy group, an aryloxy group, a hydroxyl group or ahalogen atom; more preferably a hydrogen atom, an alkyl group, an arylgroup, an alkyloxy group, an aryloxy group or a halogen atom; even morepreferably a hydrogen atom, or an alkyl group having from 1 to 12 carbonatoms; still more preferably an alkyl group having from 1 to 12 carbonatoms (preferably having from 4 to 12 carbon atoms).

R² and R⁴ are preferably a hydrogen atom, an alkyl group, an alkenylgroup, an alkynyl group, an aryl group, a substituted or unsubstitutedamino group, an alkoxy group, an aryloxy group, a hydroxyl group or ahalogen atom; more preferably a hydrogen atom, an alkyl group, an arylgroup, an alkyloxy group, an aryloxy group or a halogen atom; even morepreferably a hydrogen atom, or an alkyl group having from 1 to 12 carbonatoms; still more preferably a hydrogen atom or a methyl group; mostpreferably a hydrogen atom.

R⁵ and R⁸ are preferably a hydrogen atom, an alkyl group, an alkenylgroup, an alkynyl group, an aryl group, a substituted or unsubstitutedamino group, an alkoxy group, an aryloxy group, a hydroxyl group or ahalogen atom; more preferably a hydrogen atom, an alkyl group, an arylgroup, an alkyloxy group, an aryloxy group or a halogen atom; even morepreferably a hydrogen atom, or an alkyl group having from 1 to 12 carbonatoms; still more preferably a hydrogen atom or a methyl group; mostpreferably a hydrogen atom.

R⁶ and R⁷ are preferably a hydrogen atom, an alkyl group, an alkenylgroup, an alkynyl group, an aryl group, a substituted or unsubstitutedamino group, an alkoxy group, an aryloxy group, a hydroxyl group or ahalogen atom; more preferably a hydrogen atom, an alkyl group, an arylgroup, an alkyloxy group, an aryloxy group or a halogen atom; even morepreferably a hydrogen atom or a halogen atom; still more preferably ahydrogen atom or a chlorine atom.

Of the compounds of formula (101), more preferred are those of thefollowing formula (101-B):

wherein R¹, R³, R⁶ and R⁷ have the same meanings as those in formula(101-A), and their preferred ranges are also the same as those therein.

Specific examples of the compounds of formula (101) are mentioned below,to which, however, the invention should not be limited.

Of the benzotriazole compounds mentioned hereinabove, those having amolecular weight of not smaller than 320 are preferred. We, the presentinventors have confirmed that the compounds of the type are advantageousin point of their retentiveness in cellulose acylate films formed withthem.

Preferred examples of benzophenone compounds for use as thewavelength-dependent anisotropy distribution improver in the inventionare those of the following Formula (102):

wherein Q¹ and Q² each independently represents an aromatic ring; Xrepresents NR (where R represents a hydrogen atom or a substituent), anoxygen atom or a sulfur atom.

The aromatic ring for Q¹ and Q² may be an aromatic hydrocarbon ring oran aromatic hetero ring. It may be a single ring or may form a condensedring with any other ring.

The aromatic hydrocarbon ring for Q¹ and Q² is preferably a monocyclicor bicyclic aromatic hydrocarbon ring having from 6 to 30 carbon atoms(e.g., benzene ring, naphthalene ring), more preferably an aromatichydrocarbon ring having from 6 to 20 carbon atoms, even more preferablyfrom 6 to 12 carbon atoms. Still more preferably, it is a benzene ring.

The aromatic hetero ring for Q¹ and Q² is preferably an aromatic heteroring that contains at least any one of an oxygen atom, a nitrogen atomor a sulfur atom. Examples of the hetero-ring are furan, pyrrole,thiophene, imidazole, pyrazole, pyridine, pyrazine, pyridazine,triazole, triazine, indole, indazole, purine, thiazoline, thiazole,thiadiazole, oxazoline, oxazole, oxadiazole, quinoline, isoquinoline,phthalazine, naphthyridine, quinoxaline, quinazoline, cinnoline,pteridine, acridine, phenanthroline, phenazine, tetrazole,benzimidazole, benzoxazole, benzothiazole, benzotriazole, tetrazaindene.The aromatic hetero-ring is preferably pyridine, triazine or quinoline.

The aromatic ring for Q¹ and Q² is preferably an aromatic hydrocarbonring, more preferably an aromatic hydrocarbon ring having from 6 to 10carbon atoms, still more preferably a substituted or unsubstitutedbenzene ring.

Q¹ and Q² may have a substituent, for which preferred are thesubstituents T mentioned below. However, the substituent does notinclude a carboxylic acid, a sulfonic acid and a quaternary ammoniumsalt. If possible, the substituents may bond to each other to form acyclic structure.

X represents NR (where R represents a hydrogen atom or a substituent,and for the substituent, referred to are the substituents T mentionedbelow), an oxygen atom or a sulfur atom. X is preferably NR (where R ispreferably an acyl group or a sulfonyl group which may be substituted),or O, more preferably O.

The substituents T include, for example, an alkyl group (preferablyhaving from 1 to 20 carbon atoms, more preferably from 1 to 12 carbonatoms, even more preferably from 1 to 8 carbon atoms, e.g., methyl,ethyl, iso-propyl, tert-butyl, n-octyl, n-decyl, n-hexadecyl,cyclopropyl, cyclopentyl, cyclohexyl), an alkenyl group (preferablyhaving from 2 to 20 carbon atoms, more preferably from 2 to 12 carbonatoms, even more preferably from 2 to 8 carbon atoms, e.g., vinyl,allyl, 2-butenyl, 3-pentenyl), an alkynyl group (preferably having from2 to 20 carbon atoms, more preferably from 2 to 12 carbon atoms, evenmore preferably from 2 to 8 carbon atoms, e.g., propargyl, 3-pentynyl),an aryl group (preferably having from 6 to 30 carbon atoms, morepreferably from 6 to 20 carbon atoms, even more preferably from 6 to 12carbon atoms, e.g., phenyl, p-methylphenyl, naphthyl), a substituted orunsubstituted amino group (preferably having from 0 to 20 carbon atoms,more preferably from 0 to 10 carbon atoms, even more preferably from 0to 6 carbon atoms, e.g., amino, methylamino, dimethylamino,diethylamino, dibenzylamino), an alkoxy group (preferably having from 1to 20 carbon atoms, more preferably from 1 to 12 carbon atoms, even morepreferably from 1 to 8 carbon atoms, e.g., methoxy, ethoxy, butoxy), anaryloxy group (preferably having from 6 to 20 carbon atoms, morepreferably from 6 to 16 carbon atoms, even more preferably from 6 to 12carbon atoms, e.g., phenyloxy, 2-naphthyloxy), an acyl group (preferablyhaving from 1 to 20 carbon atoms, more preferably from 1 to 16 carbonatoms, even more preferably from 1 to 12 carbon atoms, e.g., acetyl,benzoyl, formyl, pivaloyl), an alkoxycarbonyl group (preferably havingfrom 2 to 20 carbon atoms, more preferably from 2 to 16 carbon atoms,even more preferably from 2 to 12 carbon atoms, e.g., methoxycarbonyl,ethoxycarbonyl), an aryloxycarbonyl group (preferably having from 7 to20 carbon atoms, more preferably from 7 to 16 carbon atoms, even morepreferably from 7 to 10 carbon atoms, e.g., phenyloxycarbonyl), anacyloxy group (preferably having from 2 to 20 carbon atoms, morepreferably from 2 to 16 carbon atoms, even more preferably from 2 to 10carbon atoms, e.g., acetoxy, benzoyloxy), an acylamino group (preferablyhaving from 2 to 20 carbon atoms, more preferably from 2 to 16 carbonatoms, even more preferably from 2 to 10 carbon atoms, e.g.,acetylamino, benzoylamino), an alkoxycarbonylamino group (preferablyhaving from 2 to 20 carbon atoms, more preferably from 2 to 16 carbonatoms, even more preferably from 2 to 12 carbon atoms, e.g.,methoxycarbonylamino), an aryloxycarbonylamino group (preferably havingfrom 7 to 20 carbon atoms, more preferably from 7 to 16 carbon atoms,even more preferably from 7 to 12 carbon atoms, e.g.,phenyloxycarbonylamino), a sulfonylamino group (preferably having from 1to 20 carbon atoms, more preferably from 1 to 16 carbon atoms, even morepreferably from 1 to 12 carbon atoms, e.g., methanesulfonylamino,benzenesulfonylamino), a sulfamoyl group (preferably having from 0 to 20carbon atoms, more preferably from 0 to 16 carbon atoms, even morepreferably from 0 to 12 carbon atoms, e.g., sulfamoyl, methylsulfamoyl,dimethylsulfamoyl, phenylsulfamoyl), a carbamoyl group (preferablyhaving from 1 to 20 carbon atoms, more preferably from 1 to 16 carbonatoms, even more preferably from 1 to 12 carbon atoms, e.g., carbamoyl,methylcarbamoyl, diethylcarbamoyl, phenylcarbamoyl), an alkylthio group(preferably having from 1 to 20 carbon atoms, more preferably from 1 to16 carbon atoms, even more preferably from 1 to 12 carbon atoms, e.g.,methylthio, ethylthio), an arylthio group (preferably having from 6 to20 carbon atoms, more preferably from 6 to 16 carbon atoms, even morepreferably from 6 to 12 carbon atoms, e.g., phenylthio), a sulfonylgroup (preferably having from 1 to 20 carbon atoms, more preferably from1 to 16 carbon atoms, even more preferably from 1 to 12 carbon atoms,e.g., mesyl, tosyl), a sulfinyl group (preferably having from 1 to 20carbon atoms, more preferably from 1 to 16 carbon atoms, even morepreferably from 1 to 12 carbon atoms, e.g., methanesulfinyl,benzenesulfinyl), an ureido group preferably having from 1 to 20 carbonatoms, more preferably from 1 to 16 carbon atoms, even more preferablyfrom 1 to 12 carbon atoms, e.g., ureido, methylureido, phenylureido), aphosphoramido group (preferably having from 1 to 20 carbon atoms, morepreferably from 1 to 16 carbon atoms, even more preferably from 1 to 12carbon atoms, e.g., diethylphosphoramido, phenylphosphoramido), ahydroxyl group, a mercapto group, a halogen atom (e.g., fluorine atom,chlorine atom, bromine atom, iodine atom), a cyano group, a sulfo group,a carboxyl group, a nitro group, a hydroxamic acid group, a sulfinogroup, a hydrazino group, an imino group, a heterocyclic group(preferably having from 1 to 30 carbon atoms, more preferably from 1 to12 carbon atoms, in which the hetero atom is any of nitrogen atom,oxygen atom or sulfur atom., e.g., imidazolyl, pyridyl, quinolyl, furyl,piperidyl, morpholino, benzoxazolyl, benzimidazolyl, benzothiazolyl), asilyl group (preferably having from 3 to 40 carbon atoms, morepreferably from 3 to 30 carbon atoms, even more preferably from 3 to 24carbon atoms, e.g., trimethylsilyl, triphenylsilyl). These substituentsmay be further substituted. Two or more substituents, if any, may be thesame or different. If possible, they may bond to each other to form aring.

Of the compounds of formula (102), preferred are those of the followingformula (102-A):

wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ each independentlyrepresents a hydrogen atom or a substituent.

R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ each independently represents ahydrogen atom or a substituent. For the substituent, referred to are thesubstituents T mentioned above. These substituents may have any othersubstituent. The substituents may be condensed to form a condensedcyclic structure.

R¹, R³, R⁴, R⁵, R⁶, R⁸ and R⁹ are preferably a hydrogen atom, an alkylgroup, an alkenyl group, an alkynyl group, an aryl group, a substitutedor unsubstituted amino group, an alkoxy group, an aryloxy group, ahydroxyl group or a halogen atom; more preferably a hydrogen atom, analkyl group, an aryl group, an alkyloxy group, an aryloxy group or ahalogen atom; even more preferably a hydrogen atom, or an alkyl grouphaving from 1 to 12 carbon atoms; still more preferably a hydrogen atomor a methyl group; most preferably a hydrogen atom.

R² is preferably a hydrogen atom, an alkyl group, an alkenyl group, analkynyl group, an aryl group, a substituted or unsubstituted aminogroup, an alkoxy group, an aryloxy group, a hydroxyl group or a halogenatom; more preferably a hydrogen atom, an alkyl group having from 1 to20 carbon atoms, an amino group having from 0 to 20 carbon atoms, analkoxy group having from 1 to 12 carbon atoms, an aryloxy group havingfrom 6 to 12 carbon atoms, or a hydroxyl group; even more preferably analkoxy group having from 1 to 20 carbon atoms; still more preferably analkoxy group having from 1 to 12 carbon atoms.

R⁷ is preferably a hydrogen atom, an alkyl group, an alkenyl group, analkynyl group, an aryl group, a substituted or unsubstituted aminogroup, an alkoxy group, an aryloxy group, a hydroxyl group or a halogenatom; more preferably a hydrogen atom, an alkyl group having from 1 to20 carbon atoms, an amino group having from 0 to 20 carbon atoms, analkoxy group having from 1 to 12 carbon atoms, an aryloxy group havingfrom 6 to 12 carbon atoms, or a hydroxyl group; even more preferably ahydrogen atom, or an alkoxy group having from 1 to 20 carbon atoms(preferably having from 1 to 12 carbon atoms, more preferably havingfrom 1 to 8 carbon atoms, still more preferably a methyl group);especially preferably a methyl group or a hydrogen atom.

Of the compounds of formula (102), more preferred are those of thefollowing formula (102-B):

wherein R¹⁰ represents a hydrogen atom, a substituted or unsubstitutedalkyl group, a substituted or unsubstituted alkenyl group, a substitutedor unsubstituted alkynyl group, or a substituted or unsubstituted arylgroup.

R¹⁰ is a hydrogen atom, a substituted or unsubstituted alkyl group, asubstituted or unsubstituted alkenyl group, a substituted orunsubstituted alkynyl group, or a substituted or unsubstituted arylgroup. For the substituent, referred to are the substituents T mentionedabove.

R¹⁰ is preferably a substituted or unsubstituted alkyl group, morepreferably a substituted or unsubstituted alkyl group having from 5 to20 carbon atoms, even more preferably a substituted or unsubstitutedalkyl group having from 5 to 12 carbon atoms (e.g., n-hexyl group,2-ethylhexyl group, n-octyl group, n-decyl group, n-dodecyl group,benzyl group), still more preferably a substituted or unsubstitutedalkyl group having from 6 to 12 carbon atoms (e.g., 2-ethylhexyl group,n-octyl group, n-decyl group, n-dodecyl group, benzyl group).

The compounds of formula (102) may be produced according to a knownmethod such as that described in JP-A 11-12219.

Specific examples of the compounds of formula (102) are mentioned below,to which, however, the invention should not be limited.

Preferred examples of cyano group-containing compounds for use as thewavelength-dependent anisotropy distribution improver in the inventionare those of the following Formula (103):

wherein Q¹ and Q² each independently represents an aromatic ring; X¹ andX² each independently represent a hydrogen atom or a substituent, and atleast one of these is a cyano group.

The aromatic ring for Q¹ and Q² may be an aromatic hydrocarbon ring oran aromatic hetero ring, and it may be a single ring or may form acondensed ring with any other ring.

The aromatic hydrocarbon ring is preferably a monocyclic or bicyclicaromatic hydrocarbon ring having from 6 to 30 carbon atoms (e.g.,benzene ring, naphthalene ring), more preferably an aromatic hydrocarbonring having from 6 to 20 carbon atoms, even more preferably from 6 to 12carbon atoms. Still more preferably, it is a benzene ring.

The aromatic hetero-ring is preferably one that contains a nitrogen atomor a sulfur atom as a hetero atom. Examples of the hetero-ring arethiophene, imidazole, pyrazole, pyridine, pyrazine, pyridazine,triazole, triazine, indole, indazole, purine, thiazoline, thiazole,thiadiazole, oxazoline, oxazole, oxadiazole, quinoline, isoquinoline,phthalazine, naphthyridine, quinoxaline, quinazoline, cinnoline,pteridine, acridine, phenanthroline, phenazine, tetrazole,benzimidazole, benzoxazole, benzothiazole, benzotriazole, tetrazaindene.The aromatic hetero-ring is preferably pyridine, triazine or quinoline.

The aromatic ring for Q¹ and Q² is preferably an aromatic hydrocarbonring, more preferably a benzene ring.

Q¹ and Q² may have a substituent, for which referred to are thesubstituents T mentioned below. The substituents T include, for example,an alkyl group (preferably having from 1 to 20 carbon atoms, morepreferably from 1 to 12 carbon atoms, even more preferably from 1 to 8carbon atoms, e.g., methyl, ethyl, iso-propyl, tert-butyl, n-octyl,n-decyl, n-hexadecyl, cyclopropyl, cyclopentyl, cyclohexyl), an alkenylgroup (preferably having from 2 to 20 carbon atoms, more preferably from2 to 12 carbon atoms, even more preferably from 2 to 8 carbon atoms,e.g., vinyl, allyl, 2-butenyl, 3-pentenyl), an alkynyl group (preferablyhaving from 2 to 20 carbon atoms, more preferably from 2 to 12 carbonatoms, even more preferably from 2 to 8 carbon atoms, e.g., propargyl,3-pentynyl), an aryl group (preferably having from 6 to 30 carbon atoms,more preferably from 6 to 20 carbon atoms, even more preferably from 6to 12 carbon atoms, e.g., phenyl, p-methylphenyl, naphthyl), asubstituted or unsubstituted amino group (preferably having from 0 to 20carbon atoms, more preferably from 0 to 10 carbon atoms, even morepreferably from 0 to 6 carbon atoms, e.g., amino, methylamino,dimethylamino, diethylamino, dibenzylamino), an alkoxy group (preferablyhaving from 1 to 20 carbon atoms, more preferably from 1 to 12 carbonatoms, even more preferably from 1 to 8 carbon atoms, e.g., methoxy,ethoxy, butoxy), an aryloxy group (preferably having from 6 to 20 carbonatoms, more preferably from 6 to 16 carbon atoms, even more preferablyfrom 6 to 12 carbon atoms, e.g., phenyloxy, 2-naphthyloxy), an acylgroup (preferably having from 1 to 20 carbon atoms, more preferably from1 to 16 carbon atoms, even more preferably from 1 to 12 carbon atoms,e.g., acetyl, benzoyl, formyl, pivaloyl), an alkoxycarbonyl group(preferably having from 2 to 20 carbon atoms, more preferably from 2 to16 carbon atoms, even more preferably from 2 to 12 carbon atoms, e.g.,methoxycarbonyl, ethoxycarbonyl), an aryloxycarbonyl group (preferablyhaving from 7 to 20 carbon atoms, more preferably from 7 to 16 carbonatoms, even more preferably from 7 to 10 carbon atoms, e.g.,phenyloxycarbonyl), an acyloxy group (preferably having from 2 to 20carbon atoms, more preferably from 2 to 16 carbon atoms, even morepreferably from 2 to 10 carbon atoms, e.g., acetoxy, benzoyloxy), anacylamino group (preferably having from 2 to 20 carbon atoms, morepreferably from 2 to 16 carbon atoms, even more preferably from 2 to 10carbon atoms, e.g., acetylamino, benzoylamino), an alkoxycarbonylaminogroup (preferably having from 2 to 20 carbon atoms, more preferably from2 to 16 carbon atoms, even more preferably from 2 to 12 carbon atoms,e.g., methoxycarbonylamino), an aryloxycarbonylamino group (preferablyhaving from 7 to 20 carbon atoms, more preferably from 7 to 16 carbonatoms, even more preferably from 7 to 12 carbon atoms, e.g.,phenyloxycarbonylamino), a sulfonylamino group (preferably having from 1to 20 carbon atoms, more preferably from 1 to 16 carbon atoms, even morepreferably from 1 to 12 carbon atoms, e.g., methanesulfonylamino,benzenesulfonylamino), a sulfamoyl group (preferably having from 0 to 20carbon atoms, more preferably from 0 to 16 carbon atoms, even morepreferably from 0 to 12 carbon atoms, e.g., sulfamoyl, methylsulfamoyl,dimethylsulfamoyl, phenylsulfamoyl), a carbamoyl group (preferablyhaving from 1 to 20 carbon atoms, more preferably from 1 to 16 carbonatoms, even more preferably from 1 to 12 carbon atoms, e.g., carbamoyl,methylcarbamoyl, diethylcarbamoyl, phenylcarbamoyl), an alkylthio group(preferably having from 1 to 20 carbon atoms, more preferably from 1 to16 carbon atoms, even more preferably from 1 to 12 carbon atoms, e.g.,methylthio, ethylthio), an arylthio group (preferably having from 6 to20 carbon atoms, more preferably from 6 to 16 carbon atoms, even morepreferably from 6 to 12 carbon atoms, e.g., phenylthio), a sulfonylgroup (preferably having from 1 to 20 carbon atoms, more preferably from1 to 16 carbon atoms, even more preferably from 1 to 12 carbon atoms,e.g., mesyl, tosyl), a sulfinyl group (preferably having from 1 to 20carbon atoms, more preferably from 1 to 16 carbon atoms, even morepreferably from 1 to 12 carbon atoms, e.g., methanesulfinyl,benzenesulfinyl), an ureido group preferably having from 1 to 20 carbonatoms, more preferably from 1 to 16 carbon atoms, even more preferablyfrom 1 to 12 carbon atoms, e.g., ureido, methylureido, phenylureido), aphosphoramido group (preferably having from 1 to 20 carbon atoms, morepreferably from 1 to 16 carbon atoms, even more preferably from 1 to 12carbon atoms, e.g., diethylphosphoramido, phenylphosphoramido), ahydroxyl group, a mercapto group, a halogen atom (e.g., fluorine atom,chlorine atom, bromine atom, iodine atom), a cyano group, a sulfo group,a carboxyl group, a nitro group, a hydroxamic acid group, a sulfinogroup, a hydrazino group, an imino group, a heterocyclic group(preferably having from 1 to 30 carbon atoms, more preferably from 1 to12 carbon atoms, in which the hetero atom is any of nitrogen atom,oxygen atom or sulfur atom., e.g., imidazolyl, pyridyl, quinolyl, furyl,piperidyl, morpholino, benzoxazolyl, benzimidazolyl, benzothiazolyl), asilyl group (preferably having from 3 to 40 carbon atoms, morepreferably from 3 to 30 carbon atoms, even more preferably from 3 to 24carbon atoms, e.g., trimethylsilyl, triphenylsilyl). These substituentsmay be further substituted. Two or more substituents, if any, may be thesame or different. If possible, they may bond to each other to form aring.

X¹ and X² each are a hydrogen atom or a substituent, and at least one ofthese is a cyano group. For the substituent for X¹ and X², referred toare the substituents T mentioned above. The substituent for X¹ and X²may be substituted with any other substituent, and X¹ and X² may becondensed to form a cyclic structure.

X¹ and X² are preferably a hydrogen atom, an aryl group, a cyano group,a nitro group, a carbonyl group, a sulfonyl group or an aromatic heteroring; more preferably a cyano group, a carbonyl group, a sulfonyl groupor an aromatic hetero ring; even more preferably a cyano group or acarbonyl group; still more preferably a cyano group, or analkoxycarbonyl group (—C(═O)OR where R represents an alkyl group havingfrom 1 to 20 carbon atoms, an aryl group having from 6 to 12 carbonatoms or their combination).

Of the compounds of formula (103), preferred are those of the followingformula (103-A):

wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹ and R¹⁰ each independentlyrepresents a hydrogen atom or a substituent; X¹ and X² have the samemeanings as those in formula (103), and their preferred ranges are alsothe same as those therein.

R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹ and R¹⁰ each independently representsa hydrogen atom or a substituent. For the substituent, referred to arethe substituents T mentioned above. These substituents may have anyother substituent. The substituents may be condensed to form a condensedcyclic structure.

R¹, R², R⁴, R⁵, R⁶, R⁷, R⁹ and R¹⁰ are preferably a hydrogen atom, analkyl group, an alkenyl group, an alkynyl group, an aryl group, asubstituted or unsubstituted amino group, an alkoxy group, an aryloxygroup, a hydroxyl group or a halogen atom; more preferably a hydrogenatom, an alkyl group, an aryl group, an alkyloxy group, an aryloxy groupor a halogen atom; even more preferably a hydrogen atom, or an alkylgroup having from 1 to 12 carbon atoms; still more preferably a hydrogenatom or a methyl group; most preferably a hydrogen atom.

R³ and R⁸ are preferably a hydrogen atom, an alkyl group, an alkenylgroup, an alkynyl group, an aryl group, a substituted or unsubstitutedamino group, an alkoxy group, an aryloxy group, a hydroxyl group or ahalogen atom; more preferably a hydrogen atom, an alkyl group havingfrom 1 to 20 carbon atoms, an amino group having from 0 to 20 carbonatoms, an alkoxy group having from 1 to 12 carbon atoms, an aryloxygroup having from 6 to 12 carbon atoms, or a hydroxyl group; even morepreferably a hydrogen atom, or an alkoxy group having from 1 to 12carbon atoms; still more preferably an alkoxy group having from 1 to 12carbon atoms; further preferably a hydrogen atom.

Of the compounds of formula (103), more preferred are those of thefollowing formula (103-B):

wherein R³ and R⁸ have the same meanings as those in formula (103-A),and their preferred ranges are also the same as therein; X³ represents ahydrogen atom or a substituent.

X³ represents a hydrogen atom or a substituent. For the substituent,referred to are the substituents T mentioned above. If possible, thesubstituent may be further substituted with any other substituent. X³ ispreferably a hydrogen atom, an alkyl group, an aryl group, a cyanogroup, a nitro group, a carbonyl group, a sulfonyl group or an aromatichetero ring; more preferably a cyano group, a carbonyl group, a sulfonylgroup or an aromatic hetero ring; even more preferably a cyano group ora carbonyl group; still more preferably a cyano group or analkoxycarbonyl group (—C(═O)OR where R is an alkyl group having from 1to 20 carbon atoms, an aryl group having from 6 to 12 carbon atoms ortheir combination).

Of the compounds of formula (103), even more preferred are those of thefollowing formula (103-C):

wherein R³ and R⁸ have the same meanings as those in formula (103-A),and their preferred ranges are also the same as therein; R²¹ representsan alkyl group having from 1 to 20 carbon atoms.

When R³ and R⁸ are both hydrogen atoms, then R²¹ is preferably an alkylgroup having from 2 to 12 carbon atoms, more preferably an alkyl grouphaving from 4 to 12 carbon atoms, even more preferably an alkyl grouphaving from 6 to 12 carbon atoms, still more preferably an n-octylgroup, a tert-octyl group, a 2-ethylhexyl group, an n-decyl group or ann-dodecyl group; most preferably a 2-ethylhexyl group.

When R³ and R⁸ are not hydrogen atoms, then R²¹ is preferably an alkylgroup having at most 20 carbon atoms with which the molecular weight ofthe compound of formula (103-C) could be at least 300.

The compounds of formula (103) for use in the invention can be producedaccording to the method described in Journal of American ChemicalSociety, Vol. 63, p. 3452 (1941).

Specific examples of the compounds of formula (103) are mentioned below,to which, however, the invention should not be limited.

[Mat Agent Particles]

The cellulose acylate film in the invention preferably containsparticles serving as a mat agent. The particles for use herein includesilicon dioxide, titanium dioxide, aluminium oxide, zirconium oxide,calcium carbonate, talc, clay, calcined kaolin, calcined calciumsilicate, calcium silicate hydrate, aluminium silicate, magnesiumsilicate and calcium phosphate. The particles are preferablysilicon-having ones as the haze of the films containing them may be low.Especially preferred is silicon dioxide. Particles of silicon dioxidefor use herein preferably have a primary mean particle size of at most20 nm and have an apparent specific gravity of at least 70 g/liter. Morepreferred are particles having a small primary mean particle size offrom 5 to 16 nm, since the haze of the films containing them is lower.The apparent specific gravity is more preferably from 90 to 200 g/liter,even more preferably from 100 to 200 g/liter. Particles having a largerapparent specific gravity may give a dispersion having a higherconcentration, and are therefore preferable since the haze of the filmscontaining them could be lower and since the solid deposits in the filmmay be reduced.

The particles generally form secondary particles having a mean particlesize of from 0.1 to 3.0 μm, and in the film, they exist as aggregates ofprimary particles, therefore forming protrusions having a size of from0.1 to 3.0 μm in the film surface. Preferably, the secondary meanparticle size is from 0.2 μm to 1.5 μm, more preferably from 0.4 μm to1.2 μm, most preferably from 0.6 μm to 1.1 μm. The primary and secondaryparticle sizes are determined as follows: The particles in a film areobserved with a scanning electromicroscope, and the diameter of thecircle that is circumscribed around the particle is referred to as theparticle size. 200 particles are observed at random in different sites,and their data are averaged to give the mean particle size thereof.

For silicon dioxide particles, herein usable are commercial products ofAerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (allby Nippon Aerosil). Zirconium oxide particles are also commerciallyavailable, for example, as Aerosil R976 and R811 (both by NipponAerosil), and are usable herein.

Of those, Aerosil 200V and Aerosil R972V are silicon dioxide particleshaving a primary mean particle size of at most 20 nm and having anapparent specific gravity of at least 70 g/liter, and these areespecially preferred for use herein since they are effective forreducing the friction coefficient of optical films not increasing thehaze thereof.

In the invention, for obtaining a cellulose acylate film that containsparticles having a small secondary mean particle size, there may beemployed some methods for preparing a dispersion of particles. Forexample, one method for it comprises previously preparing a dispersionof particles by stirring and mixing a solvent and particles, then addingthe resulting dispersion to a small amount of a cellulose acylatesolution separately prepared, and thereafter further mixing it with amain cellulose acylate dope. This method is desirable since thedispersibility of silicon dioxide particles is good and since thedispersion of silicon dioxide particles prepared hardly reaggregates.Apart from it, also employable herein is a method comprising adding asmall amount of a cellulose ester to a solvent, dissolving them withstirring, and fully mixing the resulting dispersion of particles with adope in an in-line mixer. The invention should not be limited to thesemethods. When silicon dioxide particles are mixed and dispersed in asolvent, the silicon dioxide concentration in the resulting dispersionis preferably from 5 to 30% by mass, more preferably from 10 to 25% bymass, most preferably from 15 to 20% by mass. Relative to the amount ofthe particles therein, the dispersion having a higher concentration mayhave a smaller haze, and is therefore favorable since the haze of thefilms with it may be lowered and the solid deposits may be reduced inthe films. Finally, the amount of the mat agent to be in the celluloseacylate dope is preferably from 0.01 to 1.0 g/m², more preferably from0.03 to 0.3 g/m², most preferably from 0.08 to 0.16 g/m².

The solvent may be a lower alcohol, preferably methyl alcohol, ethylalcohol, propyl alcohol, isopropyl alcohol or butyl alcohol. The solventusable herein except such lower alcohols is not specifically defined,for which, however, preferred are those generally used in celluloseester film formation.

[Plasticizer, Antioxidant, Release Agent]

In addition to the compound capable of lowering optical anisotropy andthe wavelength-dependent anisotropy dispersion improver mentioned above,the cellulose acylate film of the invention may contain variousadditives (e.g., plasticizer, UV inhibitor, antioxidant, release agent,IR absorbent) added thereto in the process of producing it and inaccordance with the use of the film. The additives may be solid or oily.In other words, they are not specifically defined in point of theirmelting point and boiling point. For example, UV-absorbing materials maybe mixed at 20° C. or lower and at 20° C. or higher; and the same mayapply to mixing plasticizers. For example, this is described in JP-A2001-151901. Further, IR-absorbing dyes are described in, for example,JP-A 2001-194522. The time when the additives are added may be anytimein the process of preparing dopes. As the case may be, the additives maybe added in the final step of the process of preparing dopes. The amountof each additive to be added is not specifically defined so far as theadditive could exhibit its function. When the cellulose acylate film hasa multi-layer structure, then the type and the amount of the additivesto be added to each layer may differ. For example, this is described inJP-A 2001-151902, and the technique is well known in the art. Itsdetails are described in Hatsumei Kyokai's Disclosure Bulletin No.2001-1745 (issued Mar. 15, 2001 by Hatsumei Kyokai), pp. 16-12, and thematerials described therein are preferably used in the invention.

[Blend Ratio of Compounds]

In the cellulose acylate film of the invention, the overall amount ofthe compounds having a molecular weight of at most 3000 is preferablyfrom 5 to 45% relative to the mass of cellulose acylate, more preferablyfrom 10 to 40%, even more preferably from 15 to 30%. As so mentionedhereinabove, the compounds include an compound capable of loweringoptical anisotropy, a wavelength-dependent anisotropy dispersionimprover, a UV inhibitor, a plasticizer, an antioxidant, fine particles,a release agent and an IR absorbent. Preferably, they have a molecularweight of at most 3000, more preferably at most 2000, even morepreferably at most 1000. If the overall amount of these compounds issmaller than 5%, then it may be problematic in that the properties ofthe cellulose acylate alone may be too noticeable in the film and, forexample, the optical properties and the physical strength of the filmmay readily fluctuate depending on the change of the ambient temperatureand humidity. If, however, the overall amount of the compounds is largerthan 45%, then the compounds will be over the limit of their miscibilityin the cellulose acylate film and it may be also problematic in that theexcess compounds may deposit in the film surface and the film may bethereby whitened (bleeding out from film).

[Organic Solvent in Cellulose Acylate Solution]

In the invention, the cellulose acylate film is produced preferablyaccording to a solvent-casting method, in which a cellulose acylate isdissolved in an organic solvent to prepare a solution (dope) and thedope is formed into films. The organic solvent preferably used as themain solvent in the invention is selected from esters, ketones andethers having from 2 to 12 carbon atoms, and halogenohydrocarbons havingfrom 1 to 7 carbon atoms. Esters, ketones and ethers for use herein mayhave a cyclic structure. Compounds having any two or more functionalgroups of esters, ketones and ethers (i.e., —O—, —CO— and —COO—) mayalso be used herein as the main solvent, and for example, they may haveany other functional group such as alcoholic hydroxyl group. The numberof the carbon atoms that constitute the main solvent having two or morefunctional groups may fall within the range the compound having any ofthose functional groups.

For the cellulose acylate film of the invention, chlorine-basedhalogenohydrocarbons may be used as the main solvent, or non-chlorinesolvents as in Hatsumei Kyokai's Disclosure Bulletin 2001-1745 (pp.12-16) may also be used as the main solvent. Anyhow, the main solvent isnot limitative for the cellulose acylate film of the invention.

In addition, the solvents for the cellulose acylate solution and thefilm and also methods for dissolution therein are disclosed in thefollowing patent publications, and these are preferred embodiments foruse in the invention. For example, they are described in JP-A2000-95876, 12-95877, 10-324774, 8-152514, 10-330538, 9-95538, 9-95557,10-235664, 12-63534, 11-21379, 10-182853, 10-278056, 10-279702,10-323853, 10-237186, 11-60807, 11-152342, 11-292988, 11-60752,11-60752. These patent publications disclose not only the solventspreferred for cellulose acylate for the invention but also the physicalproperties of their solutions as well as the substances that may coexistalong with them, and these are also preferred embodiments for use in theinvention.

[Method for Producing Cellulose Acylate Film]

[Dissolution Step]

Preparing the cellulose acylate solution (dope) in the invention is notspecifically defined in point of its dissolution process. It may beprepared at room temperature or may be prepared in a mode of coolingdissolution or high-temperature dissolution or in a mode of theircombination. A process comprising a step of preparing the celluloseacylate solution for use in the invention and a subsequent step ofconcentration and filtration of the solution is described in detail inHatsumei Kyokai's Disclosure Bulletin 2001-1745 (issued Mar. 15, 2001,by Hatsumei Kyokai), pp. 22-25, and this is preferably employed in theinvention.

(Transparency of Dope Solution)

Preferably, the dope transparency of the cellulose acylate solution inthe invention is at least 85%, more preferably at least 88%, even morepreferably at least 90%. We, the present inventors have confirmed thatvarious additives well dissolve in the cellulose acylate dope solutionin the invention. A concrete method for determining the dopetransparency is described. A dope solution is put into a glass cellhaving a size of 1 cm², and its absorbance at 550 nm is measured with aspectrophotometer (UV-3150 by Shimadzu). The solvent alone is measuredas a blank, and the transparency of the cellulose acylate solution iscalculated from the ratio of the solution absorbance to the blankabsorbance.

[Casting, Drying and Winding Step]

Next, a process of forming a film from the cellulose acylate solution inthe invention is described. For the method and the equipment forproducing the cellulose acylate film in the invention, herein employableare the solvent-casting method and the solvent-casting equipmentheretofore generally used in the art for cellulose triacetate filmformation. A dope (cellulose acylate solution) prepared in a dissolver(tank) is once stored in a storage tank, in which the dope is defoamedand is thus finally prepared. From the dope take-out mouth of the tank,the dope is taken out and fed into a pressure die via a meteringpressure gear pump capable of feeding it with accuracy, for example,based on the revolution number thereof, and then the dope is uniformlycast onto the endlessly-running cast member of a metal support via theslit of the pressure die, and at a peel point to which the metal supportmakes nearly one revolution, the still wet dope film (this may bereferred to as a web) is peeled from the metal support. While both endsof the thus-obtained web are clipped to ensure its width, the web isconveyed with a tenter and dried, and then further conveyed with rollsin a drier in which the web is completely dried, and thereafter this iswound up around a winder to predetermined width. The combination of thetenter and the drier with rolls may vary depending on the object of thefilm to be produced. When the essential applications of the celluloseacylate film of the invention are for functional protective films foroptical structures in electronic displays or for silver halidephotographic materials, then additional coating devices may be fitted tothe solvent casting apparatus for producing the film. The additionaldevices are for further processing the surface of the film by formingthereon a subbing layer, an antistatic layer, an antihalation layer anda protective layer. This is described in detail in Hatsumei Kyokai'sDisclosure Bulletin 2001-1745 (issued Mar. 15, 2001, by HatsumeiKyokai), pp. 25-30. It includes casting (including co-casting), metalsupport, drying and peeling, and these are preferably employed in theinvention.

Preferably, the thickness of the cellulose acylate film of the inventionis from 10 to 120 μm, more preferably from 20 to 100 μm, even morepreferably from 30 to 90 μm.

[Change in Optical Performance of Film after High-Humidity Treatment]

[Evaluation of Physical Properties of Cellulose Acylate Film]

Concerning a change in the optical performance of the cellulose acylatefilm of the invention due to an environmental change, it is desirablethat the film having been treated at 60° C. and 90% RH for 240 hoursshows changes in Re(400), Re(700), Rth(400) and Rth(700) of not morethan 15 nm, more preferably not more than 12 nm and more preferably notmore than 10 nm.

[Change in Optical Performance of Film after High-Temperature Treatment]

Also, it is desirable that the film having been treated at 80° C. for240 hours shows changes in Re(400), Re(700), Rth(400) and Rth(700) ofnot more than 15 nm, more preferably not more than 12 nm and morepreferably not more than 10 nm.

[Amount of Vaporized Compound after Heat Treatment of Film]

It is desirable that a Rth-lowering compound and a ΔRth-loweringcompound preferably in the invention are vaporized at a ratio of notmore than 30%, more preferably not more than 25% and more preferably notmore than 20%, after treating the film at 80° C. for 240 hours.

The amount of the compounds evaporated from the film is determined bydissolving the film having been treated at 80° C. for 240 hours and theuntreated film in a solvent, detecting the compounds from each sample byhigh-performance liquid chromatography, and calculating in accordancewith the following formula by referring the peak area of the compound asthe amount thereof remaining in the film.Vaporization amount(%)={(amount of compound remaining in untreatedsample)−(amount ofcompound remaining in treated sample)}/(amount of compound remaining inuntreatedsample)×100[Glass Transition Temperature Tg of Film]

The glass transition temperature Tg of the cellulose acylate film in theinvention falls between 80 and 165° C. From the viewpoint of the heatresistance of the film, Tg preferably falls between 100 and 160° C.,more preferably between 110 and 150° C. The glass transition temperatureTg is determined as follows: 10 mg of a sample of the cellulose acylatefilm of the invention is heated from room temperature up to 200° C. at aheating rate of 5° C./min, and the quantity of heat of the sample ismeasured with a differential scanning calorimeter (DSC 2910 by T.A.Instrument), and the glass transition temperature Tg of the film iscalculated from it.

[Haze of Film]

Preferably, the haze of the cellulose acylate film in the inventionfalls between 0.01 and 2.0%, more preferably between 0.05 and 1.5%, evenmore preferably between 0.1 and 1.0%. The film transparency is a matterof importance when the film serves as an optical film. The haze may bedetermined as follows: A sample of the cellulose acylate film of theinvention having a size of 40 mm×80 mm is measured with a haze meter(HGM-2DP by Suga Test Instruments) at 25° C. and 60% RH, according toJIS K-6714.

[Humidity-Dependencies of Re and Rth of Film]

It is preferable that both of the in-plane retardation Re(λ) and thethickness-direction retardation Rth(λ) of the cellulose acylate film ofthe invention show little changes depending on humidity. Morespecifically speaking, it is preferable that the difference ΔRth(400)between Rth(400) at 25° C. and 10% RH and Rth(400) at 25° C. and 80% RH(i.e., ΔRth(400)=Rth(400)10% RH-Rth(400)80% RH) ranges from 0 to 50 nm,more preferably from 0 to 40 nm and more preferably from 0 to 35 nm. Itis also preferable that ΔRth(700) falls within the same range. It ispreferable that the difference ΔRe(400) between Re(400) at 25° C. and10% RH and Re(400) at 25° C. and 80% RH (i.e., ΔRe(400)=Re(400)10%RH−Re(400)80% RH) ranges from 0 to 10 nm, more preferably from 0 to 5 nmand more preferably from 0 to 2 nm. It is also preferable that ΔRe(700)falls within the same range.

[Equivalent Water Content of Film]

The equivalent water content of the cellulose acylate film in theinvention is described. When the film is used as a protective film forpolarization films, then the equivalent water content thereof at 25° C.and 80% RH is preferably from 0 to 4%, more preferably from 0.1 to 3.5%,even more preferably from 1 to 3% irrespective of the film thickness, inorder not to detract from the adhesiveness of the film to water-solublepolymer such as polyvinyl alcohol. If the equivalent water content ishigher than 4%, then it is undesirable since the humidity-dependentretardation of the film may be too great when the film is used as asupport for optically-compensatory films.

The water content is determined as follows: A sample of the celluloseacylate film of the invention having a size of 7 mm×35 mm is analyzedwith a water content analyzer combined with a sample drier (CA-03,VA-05, both by Mitsubishi Chemical), according to a Karl-Fisher method.The amount of water (g) in the sample thus measured is divided by theweight of the sample (g).

[Moisture Permeability of Film]

Preferably, the moisture permeability of the cellulose acylate film tobe used for optically-compensatory sheets of the invention, asdetermined at a temperature of 60° C. and at a humidity of 95% RHaccording to JIS Z0288 and converted in terms of a standard filmthickness of 80 μm, is from 400 to 2000 g/m²·24 h, more preferably from500 to 1800 g/m²·24 h, even more preferably from 600 to 1600 g/m²·24 h.If it is over than 2000 g/m²·24 h, then the humidity-dependent absolutevalues Re and Rth of the film may be significantly higher than 0.5 nm/%RH. In addition, it is also unfavorable when an optically-anisotropiclayer is laminated on the cellulose acylate film of the type of theinvention to fabricate an optically-compensatory film, since thehumidity-dependent absolute values Re and Rth of the sheet may also besignificantly higher than 0.5 nm/% RH. When the optically-compensatorysheet or the polarization film of the type is built in liquid-crystaldisplay devices, then it may cause discoloration and viewing anglereduction. On the other hand, if the moisture permeability of thecellulose acylate film is smaller than 400 g/m²·24 h, then the film mayinterfere with drying of adhesive when it is stuck to both faces of apolarizing film to fabricate a polarization film, or that is, the filmmay cause adhesion failure in the polarization film.

When the thickness of the cellulose acylate film is larger, then themoisture permeability thereof may be smaller; and when the thickness issmaller, then the moisture permeability may be larger. Accordingly, themoisture permeability of every sample having a different thickness mustbe determined, as converted in terms of a standard film thickness of 80μm. Depending on the film thickness thereof, the moisture permeabilityof the film is determined as follows: Moisture permeability as convertedin terms of standard film thickness of 80 μm=(measured moisturepermeability)×(measured film thickness μm/80 μm). Regarding the methodof measuring the moisture permeability, referred to are the methodsdescribed in Physical Properties of Polymer II (Polymer ExperimentalLecture 4, Kyoritsu Publishing), pp. 285-297, “Determination of VaporPermeation (mass method, temperature method, vapor pressure method,adsorption method)”. Briefly, a sample of the cellulose acylate filmhaving a size of 70 mmφ is conditioned at 25° C. and 90% RH, and at 60°C. and 95% RH both for 24 hours. Using a permeability tester (KK-709007by Toyo Seiki), the water content per unit area of the sample ismeasured (g/m²) according to JIS Z-0208, and the moisture permeabilityof the sample is calculated as follows: Moisture permeability=weight ofconditioned sample−weight of unconditioned sample.

[Dimensional Change of Film]

The dimensional stability of the cellulose acylate film of the inventionis preferably as follows: The dimensional change of the film afterstored at 60° C. and 90% RH for 24 hours (high-humidity storage), andthe dimensional change of the film after stored at 90° C. and 5% RH for24 hours (high-temperature storage) are both at most 0.5%. Morepreferably, the dimensional change is at most 0.3%, even more preferablyat most 0.15%.

A concrete method for the measurement is described. Two samples of thecellulose acylate film of the invention, having a size of 30 mm×120 mm,are prepared and conditioned at 25° C. and 65% RH for 24 hours. Using anautomatic pin gauge (by Shinto Kagaku), holes of 6 mmφ are formed onboth sides of the samples each at intervals of 100 mm. The originalhole-to-hole distance is L0. One sample is processed at 60° C. and 90%RH for 24 hours, and then the hole-to-hole distance is measured (L1);and the other sample is processed at 90° C. and 5% RH for 24 hours, andthe hole-to-hole distance is measured (L2). The minimum gauge limit inevery measurement is 1/1000 mm. The dimensional change is determined asfollows:Dimensional change at 60° C. and 90% RH(high-humiditystorage)={|L0−L1|/L0}×100.Dimensional change at 90° C. and 5% RH(high-temperaturestorage)={|L0−L2|/L0}×100.[Sound Velocity of Film]

Concerning the sound velocity of the cellulose acylate film of theinvention, the absolute value is not specifically restricted. However,it is desirable that the ratio R (VT/VM) of the sound velocity in thetransverse direction VT to the sound velocity in the machine directionVM is from 1.05 to 1.50.

It is more preferred that the ratio is from 1.06 to 1.45, morepreferably from 1.07 to 1.40. When this ratio exceeds 1.50, curling andoptical performance are largely changed in a durability test. The soundvelocity is measured in practice by a method which comprisesconditioning the film in an atmosphere at 25° C. and 55% RH for 6 hoursor longer with the use of a sound velocity measurement device SST-110(manufactured by NOMURA), measuring the sound velocity in the transversedirection and the sound velocity in the machine direction at 25° C. and55% RH and then determining the ratio.

[Tensile Modulus of Film]

The tensile modulus in the transverse direction of the cellulose acylatefilm of the invention ranges from 240 to 600 kgf/mm² (2.35 GPa to 5.88GPa), preferably from 250 to 580 kgf/mm² (2.45 GPa to 5.68 GPa). Thetensile modulus in the machine direction of the cellulose acylate filmof the invention ranges from 230 to 480 kgf/mm² (2.25 GPa to 4.70 GPa),preferably from 240 to 470 kgf/mm² (2.35 GPa to 4.61 GPa). It isdesirable that a ratio of the former tensile modulus in the transversedirection to the latter tensile modulus in the machine direction(former/latter) of from 1.17 to 1.40.

The tensile is determined in practice by measuring the stress at a 0.5%elongation at a tensile speed of 10%/min in an atmosphere at 23° C. and70% RH with the use of a multipurpose tensile test machine STM T50BP(manufactured by TOYO BALDWIN).

[Storage Modulus of Film]

It is desirable that the storage modulus in the transverse direction andthe storage modulus in the machine direction of the cellulose acylatefilm of the invention are both from 15000 to 80000 kfg/cm² (1.47 GPa to7.84 GPa) and a ratio of the former storage modulus in the transversedirection to the latter storage modulus in the machine direction(former/latter) of from 1.15 to 1.80.

It is more preferable that the storage modulus in the transversedirection and the storage modulus in the machine direction are both from18000 to 75000 kfg/cm² (1.76 GPa to 7.35 GPa) and a ratio of the formerstorage modulus in the transverse direction to the latter storagemodulus in the machine direction (former/latter) of from 1.16 to 1.60.It is further preferable that the storage modulus in the directionorthogonal to the traveling direction in the film plane and the storagemodulus in the traveling direction are both from 20000 to 70000 kfg/cm²(1.96 GPa to 6.86 GPa) and a ratio of the former storage modulus in thetransverse direction to the latter storage modulus in the machinedirection (former/latter) of from 1.17 to 1.40.

The storage modulus is determined in practice by measuring the dynamicviscoelasticity while changing temperature.

[Photoelasticity Coefficient of Film]

The photoelasticity coefficient in the transverse direction and thephotoelasticity coefficient in the machine direction of celluloseacylate film of the invention are both preferably not more than 25×10⁻¹³cm²/dyne(2.5×10⁻¹³N/m²). The ratio of the former coefficient ofphotoelasticity in the transverse direction to the coefficient ofphotoelasticity in the machine direction (former/latter) is preferablyfrom 0.60 to 0.97.

It is more preferable that the coefficient of photoelasticity in thedirection orthogonal to the traveling direction in the film plane andthe coefficient of photoelasticity in the traveling direction are bothnot more than 22×10⁻¹³ cm²/dyne(2.2×10⁻¹³N/m²) and a ratio of the formercoefficient of photoelasticity in the transverse direction to the lattercoefficient of photoelasticity in the machine direction (former/latter)of from 0.65 to 0.96.

It is more preferable that the coefficient of photoelasticity in thedirection orthogonal to the traveling direction in the film plane andthe coefficient of photoelasticity in the traveling direction are bothnot more than 20×10⁻¹³ cm²/dyne(2.0×10⁻¹³N/m²) and a ratio of the formercoefficient of photoelasticity in the transverse direction to the lattercoefficient of photoelasticity in the machine direction (former/latter)of from 0.70 to 0.95.

The coefficient of photoelasticity is measured in practice by applying atensile stress in the transverse direction or the machine direction to afilm sample (12 mm×120 mm) and measuring the retardation with anellipsometer (M150 manufactured by JASCO ENGINEERING). Then thecoefficient of photoelasticity is calculated based on the change inretardation due to the stress.

[In-Plane Retardation Change Before and after Stretching and Detectionof Slow Axis]

From a film band, a sample (100 mm in machine direction×100 mm intransverse direction) is cut out and stretched in parallel to themachine direction (MD) or to the transverse direction (TD) with the useof a fixed monoaxial stretching machine at a temperature of 140° C. Thein-plane retardation Re of each sample is measured before and after thestretching with the use of by an automatic birefringence analyzer(KOBRA-21ADH, manufactured by Oji Science Instruments). Slow axis isdetermined based on the orientation angle obtained in the retardationmeasurement as described above. It is preferred that a cellulose acylatefilm to be provided immediately close to a polarization film shows asmall change in Re due to stretching. More specifically speaking, it ispreferable that the film shows |Re(n)−Re(0)|/n≦1.0 or less and morepreferably |Re(n)−Re(0)|n≦0.3 or less, wherein Re(n) means the in-planeretardation (nm) of the film having been stretched by n(%), while Re(0)means the in-plane retardation (nm) of the unstretched film.

[Direction Having Slow Axis]

In the case of using the cellulose acylate film of the invention as apolarization film-protecting film, the polarization film has anabsorption axis in the machine direction (MD) and thus it is preferablethat the cellulose acylate film has a slow axis in the direction closeto the MD or close to the TD. By locating the slow axis in parallel ororthogonal to the polarization film, light-leakage or color change canbe lessened. The term “close to” means that the angle between the slowaxis and MD or TD is from 0 to 10°, preferably from 0 to 5°.

[Cellulose Acylate Film Having Positive Intrinsic Birefringence]

The cellulose acylate film of the invention shows an increase in thein-plane retardation Re when stretched in the direction having the slowaxis in plane, while it shows a decrease in the in-plane retardation Rewhen stretched in the direction orthogonal to the direction having theslow axis. These facts indicate that this film has a positive intrinsicbirefringence. To eliminate Re exhibited in the film, it is effective tostretch the film in the direction orthogonal to the slow axis. This maybe achieved by, for example, lowering the in-plane retardation Re bytenter stretching in the direction orthogonal to MD (i.e., TD) in thecase where the film has the slow axis in MD. In the case where the filmhas the slow axis in TD, on the contrary, it may be suggested to lowerthe in-plane retardation Re by stretching the film while enhancing thetension of a traveling roll in parallel to the MD.

The physical properties as described above can be established each byappropriately controlling the orientation treatment conditions in thestretching treatment, the shrinking treatment, etc. as will be discussedhereinafter.

[Method of Evaluating the Cellulose Acylate Film of the Invention]

The cellulose acylate film of the invention is evaluated by using thefollowing measurement methods.

(In-Plane Retardation Value Re and Thickness-Direction Retardation ValueRth)

Re(λ) is measured by the incidence of a ray of λ nm in wavelength in thenormal direction with the use of an automatic double refractometer KOBRA21 ADH (manufactured by OJI KEISOKU KIKI). Rth(λ) is calculated withKOBRA 21 ADH based on three retardation values measured in threedirections, i.e., Re(λ) as described above, a retardation value measuredby the incidence of a ray of λ nm in wavelength in a direction incliningat +40° to the normal direction of the film using the slow axis in theplane as the incline angle and a retardation value measured by theincidence of a ray of λ nm in wavelength in a direction inclining at−40° to the normal direction of the film using the slow axis in theplane as the incline angle and a presumptive average refractive indexand the film thickness. As the presumptive average refractive index, usecan be made of values listed in POLYMER HANDBOOK (JOHN WILEY & SONS,INC) and various optical film catalogs. In the case where thepresumptive average refractive index is unknown, it can be measured withthe use of an Abbe refractometer. The presumptive average refractiveindexes of major optical films are as follows: cellulose acylate (1.48),cycloolefin polymer (1.52), polycarbonate (1.59), polymethylmethacrylate (1.49) and polystyrene (1.59). By inputting such anpresumptive average refractive index and a film thickness, nx, ny and nzcan be calculated with KOBRA 21 ADH.

(Transmittance)

By using a transparency meter (AKA phototube chronometer, manufacturedby KOTAKI SEISAKUSHO), the visible light (615 nm) transmittance of asample (20 mm×70 mm) is measured at 25° C. and 60% RH.

[Surface Property of Film]

(Surface Shape)

The surface property of the cellulose acylate film of the invention isdescribed. Preferably, the arithmetic mean roughness (Ra) of the surfaceroughness of the film, according to JIS B0601-1994, is at most 0.1 μm,and the maximum height (Ry) thereof is at most 0.5 μm. More preferably,the arithmetic mean roughness (Ra) is at most 0.05 μm, and the maximumheight (Ry) is at most 0.2 μm. The profile of the recesses and theprojections of the film surface may be analyzed with an atomic forcemicroscope (AFM).

(Surface Energy)

The surface energy of the cellulose acylate film of the invention ismeasured as follows: A sample of the film is put on a horizontal bedhorizontally thereto, and a predetermined amount of water and methyleneiodide are applied onto the surface of the sample. After a predeterminedperiod of time, the contact angle of the film surface with water andwith methylene iodide is measured. From the data of the thus-measuredcontact angle, the surface energy of the sample is derived according toan Owens method.

[In-Plane Retardation Scattering of Cellulose Acylate Film]

It is desirable that the cellulose acylate film of the inventionsatisfies the following formulae.|Re(Max)−Re(MIN)|≦3 and |Rt(MAX)−Rth(MIN)|≦5wherein Re(MAX) and Rth(MAX) mean each the maximum retardation of a filmpiece (1 m×1 m) cut out at random, while Re(MIN) and Rth(MIN) mean eachthe minimum retardation thereof.[Additive Retentiveness in Film]

The cellulose acylate film of the invention is required to well retainvarious compounds added thereto. Concretely, when the cellulose acylatefilm is stored at 80° C. and 90% RH for 48 hours, the mass change of thefilm is preferably from 0 to 5%, more preferably from 0 to 3%, even morepreferably from 0 to 2%.

<Method of Evaluation of Additive Retentiveness in Film>

A sample is cut into a size of 10 cm×10 cm, and stored at 23° C. and 55%RH for 24 hours, and its mass is measured. Then, this is stored at 80±5°C. and 90±10% RH for 48 hours. After processed, the surface of thesample is gently wiped, and then further stored at 23° C. and 55% RH for1 day, and the mass of the sample is again measured. The additiveretentiveness in the sample is calculated as follows:Additive Retentiveness(mass %)={(mass before storage−mass after storage)/(mass before storage)}×100.[Mechanical Characteristics of Film](Curl)

The curl value in the width direction of the cellulose acylate film ofthe invention is preferably from −10/m to +10/m. The cellulose acylatefilm is subjected to surface treatment as will be mentioned hereinunder,or rubbed before coated with an optically-anisotropic layer, or coatedor laminated with an orientation layer or an optically-anisotropiclayer. For these treatments, the film is processed while it is a longfilm. If the curl value of the long, cellulose acylate film in the widthdirection thereof falls outside the scope as above, then the film may bedifficult to handle and it may be cut or broken. If so, in addition, theedges and the center part of the film may be strongly contacted withconveyor rolls to give dust, and, as a result, much impurity may depositon the film. In that condition, the frequency of spot defects andcoating streaks may be over the acceptable level. In addition, when thecurl value is controlled to fall within the defined range, then it isfavorable since a trouble of color mottles that may often occur whencoated with an optically-anisotropic layer may be reduced, and, inaddition, the film may be prevented from catching bubbles when laminatedwith a polarizing film.

The curl value may be determined according to the method defined by theAmerican National Standard Institute (ANSI/ASCPH1.29-1985).

(Tear Strength)

Preferably, the cellulose acylate film of the invention having athickness of from 20 to 80 μm has a tear strength of at least 2 g,measured according to the tear test method of JISK7128-2:1998 (Elmendorftear test method), more preferably from 5 to 25 g, even more preferablyfrom 6 to 25 g. Also preferably, the tear strength of the film having athickness of 60 μm is at least 8 g, more preferably from 8 to 15 g.Concretely, a sample piece having a size of 50 mm×64 mm is conditionedat 25° C. and 65% RH, and then tested with a light load tear strengthtester to measure its tear strength.

[Solvent Remaining in Film]

It is desirable that the cellulose acylate film of the invention isdried under the condition under which the solvent amount remaining inthe film could be from 0.01 to 1.5% by mass, more preferably from 0.01to 1.0% by mass. The solvent amount to remain in the transparent supportfor use in the invention is controlled to at most 1.5%, whereby the filmcurling may be reduced. More preferably, it is at most 1.0%. Theessential reason for it may be because, since the solvent amount toremain in the film formed according to the above-mentioned solventcasting method is reduced, the free volume of the film could be reduced.

[Moisture-Absorbing Expansion Coefficient of Film]

Preferably, the moisture-absorbing expansion coefficient of thecellulose acylate film of the invention is at most 30×10⁻⁵/% RH, morepreferably at most 15×10⁻⁵/% RH, even more preferably at most 10×10⁻⁵/%RH. The moisture-absorbing expansion coefficient of the film ispreferably smaller, but in general, it may be at least 1.0×10⁻⁵/% RH.The moisture-absorbing expansion coefficient means the change of thelength of a sample when the relative humidity around the sample ischanged at a constant temperature. When the moisture-absorbing expansioncoefficient is controlled as above and when the cellulose acylate filmof the invention is used as a support for optically-compensatory films,then frame-like transmittance increase, or that is, strain-caused lightleakage can be prevented while the optically-compensatory function ofthe optically-compensatory films is kept as such.

[Functional Layer]

The applications of the cellulose acylate film of the invention includeoptical applications and photographic materials. The opticalapplications of the film are especially preferably for liquid-crystaldisplay devices, more preferably those that comprise a liquid-crystalcell carrying liquid crystal between two electrode substrates, twopolarization films disposed on both sides thereof, and at least oneoptically-compensatory sheet disposed between the liquid-crystal celland the polarization film. For the liquid-crystal display devices,preferred are TN, IPS, FLC, AFLC, OCB, STN, ECB, VA and HAN.Particularly, IPS and VA are preferred.

When the cellulose acylate film of the invention is used for theseoptical applications, various functional layers may be added to it. Thelayers are, for example, antistatic layer, cured resin layer(transparent hard coat layer), antireflection layer, easily-adhesivelayer, antiglare layer, optically-compensatory layer, orientation layer,liquid-crystal layer. These functional layers and their materials thatmay be used for the cellulose acylate film of the invention includesurfactant, lubricant, mat agent, antistatic layer and hard coat layer,and they are described in detail in Hatsumei Kyokai's DisclosureBulletin 2001-1745 (issued Mar. 15, 2001, by Hatsumei Kyokai), pp.32-45, and are preferably used also in the invention.

[Usage (Polarizing Plate)]

Next, the usage of the cellulose acylate film of the invention will bedescribed.

The cellulose acylate film of the invention is particularly useful as aprotective film for polarizing plates. A polarizing plate is composed ofa polarization film and protecting films protecting both faces thereof.It further has a protect film on one face of the polarizing plate and aseparate film on the opposite face. The protect film and the separatefilm are employed in order to protect the polarizing plate duringshipment, product inspection and other steps. In this case, theprotective film, which aims at protecting the surface of the polarizingplate, is bonded to the face opposite to the face to be bonded to aliquid crystal plate. On the other hand, the separate film, which aimsat covering the adhesive layer to be bonded to the liquid crystal plate,is bonded to the face of the polarizing plate to be bonded to the liquidcrystal face. As the protect film, use may be made of the celluloseacylate film of the invention.

As the polarization film, it is preferred to employ a coating typepolarization film typified by products of OPTIVA or a polarization filmcomprising a binder with iodine or a dichroic dye.

In a polarization film, iodine and a dichroic dye are oriented in abinder to exhibit polarization performance. It is preferable that iodineand the dichroic dye are oriented along a binder molecule or thedichroic dye is oriented in a single direction through self-organizationas in liquid crystals.

Polarization films commonly employed in these days are usually producedby dipping a stretched polymer in a solution of iodine or a dichroic dyecontained in a tank so as to allow iodine or the dichroic dye topenetrate into a binder. In a polarization film commonly employed,iodine or a dichroic dye is distributed in a depth of 4 μm (i.e., 8 μmin total in both sides) from the surface. To establish a sufficientpolarization performance, a thickness of at least 10 μm is required. Thepenetration degree can be regulated by appropriately controlling theconcentration of the solution of iodine or the dichroic dye, the tanktemperature and the dipping time.

The binder of the polarization film may be crosslinked. As a crosslinkedbinder, it is possible to use a polymer crosslinkable per se. Due tolight, heat or pH change, a polymer having a functional group or abinder obtained by introducing a functional group into a polymerundergoes a crosslinkage reaction among the molecules thereof and thus apolarization film can be formed.

Alternatively, a crosslinked structure may be introduced into a polymerby using a crosslinking agent. By using a crosslinking agent which is ahighly reactive compound, a linking group originating in thecrosslinking group is introduced into binder molecules. Thus, acrosslinked structure can be formed among the binder molecules.

Crosslinkage is generally performed by coating a coating solutioncontaining a polymer or a mixture of a polymer with a crosslinking agenton a transparent support and then heating. Since it is sufficient thatthe durability is ensured in the step of providing a final product, thecrosslinkage treatment may be carried out at any step for constructingthe polarizing plate as the final product.

As the binder of the polarization film, it is possible to use any ofpolymers crosslinkable per se or polymers capable of undergoingcrosslinkage by using a crosslinking agent. Examples of the polymersinclude polymethyl methacrylate, polyacrylic acid, polymethacrylic acid,polystyrene, gelatin, polyvinyl alcohol, denatured polyvinyl alcohol,poly(N-methylolacrylamide), polyvinyltoluene, chlorosulfonatedpolyethylene, nitrocellulose, chlorinated polyolefins (for example,polyvinyl chloride), polyester, polyimide, polyvinyl acetate,polyethylene, carboxymethylcellulose, polypropylene, polycarbonate andcopolymers thereof (for example, acrylic acid/methacrylic acidcopolymer, styrene/maleimide copolymer, styrene/vinyltoluene copolymer,vinyl acetate/vinyl chloride copolymer, ethylene/vinyl acetatecopolymer). It is preferable to use water-soluble polymers (for example,poly(N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinylalcohol and denatured polyvinyl alcohol), gelatin, polyvinyl alcohol anddenatured polyvinyl alcohol are more preferable and polyvinyl alcoholand denatured polyvinyl alcohol are most preferable.

The saponification degrees of polyvinyl alcohol and denatured polyvinylalcohol preferably ranges from 70 to 100%, more preferably from 80 to100% and most preferably from 95 to 100%. The polymerization degree ofpolyvinyl alcohol preferably ranges from 100 to 5000.

A denatured polyvinyl alcohol is obtained by introducing a denaturinggroup into polyvinyl alcohol by copolymerization denaturing,chain-transfer denaturing or block polymerization denaturing. In thecopolymerization denaturing, it is possible to introduce, as adenaturing group, COONa, Si(OH)₃, N(CH₃)3Cl, C₉H₁₉COO, SO₃Na or C₁₂H₂₅.In the chain transfer denaturing, it is possible to introduce, as adenaturing group, COONa, SH or SC₁₂H₂₅. The polymerization degree ofdenatured polyvinyl alcohol preferably ranges from 100 to 3000.Denatured polyvinyl alcohols are described in JP-A-8-338913,JP-A-9-152509 and JP-A-9-316127.

It is especially preferred to use undenatured polyvinyl alcohol andalkylthio-denatured polyvinyl alcohol having a saponification degree of85 to 95%.

Use may be made of a combination of two or more of polyvinyl alcoholsand denatured polyvinyl alcohols.

By adding a crosslinking agent for the binder in a large amount, themoisture/heat resistance of the polarization film can be improved. Inthe case where the crosslinking agent is added in an amount of 50% bymass or more based on the binder, however, the orientation properties ofiodine or a dichroic dye are worsened. It is preferable to add thecrosslinking agent in an amount of from 0.1 to 20% by mass, morepreferably from 0.5 to 15% by mass, based on the binder.

After the completion of the crosslinkage, the binder still contains theunreacted crosslinking agent in a certain amount. However, it ispreferable that the amount of the crosslinking agent remaining in thebinder is not more than 1.0% by mass, more preferably not more than 0.5%by mass. In the case where the binder layer contains more than 1.0% bymass of the crosslinking agent, there sometimes arises a problem indurability. That is to say, in the case where a polarization film havinga large amount of a crosslinking agent remaining therein is applied to aliquid-crystal display device which is then operated over a long time orallowed to stand in an atmosphere at a high temperature and a highhumidity over a long time, the polarization degree is lowered in somecases. Crosslinking agents are described in U.S. Reissue Pat. No.23,297. Moreover, it is also possible to use boron compounds (forexample, boric acid and borax) as the crosslinking agent.

As the dichroic dye, use can be made of azo-based dyes, stilbene baseddyes, pyrazolone based dyes, triphenylmethane based dyes, quinolinebased dyes, oxazine based dyes, thiazine based dyes or anthraquinonebased dyes. It is preferable that the dichroic dye is soluble in water.It is also preferable that the dichroic dye has a hydrophilicsubstituent (for example, sulfo, amino or hydroxyl). Examples of thedichroic dye include C.I. Direct Yellow 12, C.I. Direct Orange 39, C.I.Direct Orange 72, C.I. Direct Red 39, C.I. Direct Red 79, C.I. DirectRed 81, C.I. Direct Red 83, C.I. Direct Red 89, C.I. Direct Violet 48,C.I. Direct Blue 67, C.I. Direct Blue 90, C.I. Direct Green 59 and C.I.Acid Red 37. Dichroic dyes are described in JP-A-1-161202,JP-A-1-172906, JP-A-1-172907, JP-A-1-183602, JP-A-1-248105,JP-A-1-265205 and JP-A-7-261024. The dichroic dye is employed in theform of a free acid, an alkali metal salt, an ammonium salt or an aminesalt, By blending dichroic dye of two or more types, polarization filmshaving various color hues can be produced. It is preferable to use apolarization film having a compound (a dye) showing a black color or apolarization film or a polarizing plate wherein multiple dichroicmolecules are blended so as to show a black color when two polarizationaxes are orthogonalized, since such a polarization film is excellent insingle plate transmittance and polarizing ratio.

(Constitution of Liquid Crystal Display Device)

In a common liquid-crystal display device, a liquid-crystal cell isprovided between a pair of polarizing plates. A protecting film with theuse of the cellulose acylate film of the invention may be provided atany part to give excellent display performance. Since a protecting filmfor the outermost face of the polarizing plate in the display side of aliquid-crystal display device has a transparent hard coat layer, anantiglare layer, an antireflection layer, etc., it is particularlypreferable to use the above protecting film in this part.

To use the cellulose acylate film of the invention as a polarizationfilm-protecting film (a polarizing plate-protecting film) inconstructing the polarizing plate of the invention, it is necessary toachieve favorable adhesiveness between the surface in the side to bebonded to the polarization film and the polarization film comprisingpolyvinyl alcohol as the main component. When the adhesiveness isinsufficient, there arise some problems, for example, the workability ofthe polarizing plate in using a panel of a liquid-crystal display deviceor the like becomes poor or the durability is insufficient, therebyinducing some troubles such as peeling in prolonged use. For theadhesion, use may be made of a pressure-sensitive adhesive. As thepressure-sensitive adhesive, use can be made of, for example, polyvinylalcohol based pressure-sensitive adhesives containing polyvinyl alcoholor polyvinyl butyral, and vinyl based latexes containing butyl acrylate,etc. The adhesiveness may be considered by using surface energy as anindication. In the case where the surface energy of polyvinyl alcoholserving as the main component of the polarization film or thepressure-sensitive layer comprising a pressure-sensitive agentcontaining polyvinyl alcohol or vinyl based latex as the main componentis close to the surface energy of the protecting film to be bondedthereto, the bonding properties as well as the workability anddurability of the polarizing plate thus bonded can be improved. Thesefacts indicate that a sufficient adhesiveness to the polarization filmcomprising polyvinyl alcohol as the main component can be obtained bycontrolling the surface energy in the side to be bonded to thepolarization film or the pressure-sensitive adhesive layer within adesired range by a surface treatment such as hydrophilication.

Since the cellulose acylate film of the invention usually containsadditives such as a compound capable of lowering optical anisotropy anda wavelength dispersion regulator, the film face becomes morehydrophobic. It is therefore needed to improve the bonding properties bythe above-described hydrophilication to impart favorable workability anddurability to the polarizing plate.

Due to the addition of the additives as described above, the film afterthe film formation has a hydrophobic nature before the surface treatmentsuch as hydrophilication. From the viewpoints of the humidity-dependenceof the optical characteristics or mechanical characteristics of the filmand easiness in the treatment for improving the bonding properties asdiscussed above, it is preferable that the surface energy of the film is30 mN/m or more but not more than 50 mN/m, more preferably 40 mN/m ormore but not more than 48 mN/m. In the case where the surface energybefore the treatment is less than 30 mN/m, much energy is needed toachieve favorable bonding properties by the hydrophilication as will bedescribed hereinafter. In this case, as a result, the film propertiesare worsened or the favorable properties and a high productivity can behardly established at the same time. When the surface energy before thetreatment exceeds 50 mN/m, the hydrophilic nature of the film per sebecomes too high and, in its turn, the optical performance andmechanical properties of the film excessively depend on humidity tothereby cause some problems.

The surface energy of polyvinyl alcohol face ranges from 60 mN/m to 80mN/m, though it varies depending on the additives to be used together,the extent of drying and the pressure-sensitive additive employed. Thus,it is preferable that the surface energy of the face of the film of theinvention in the side to be bonded to the polarization film after thesurface treatment such as hydrophilication is 50 mN/m or more but notmore than 80 mN/m, more preferably 60 mN/m or more but not more than 75mN/m and more preferably 65 mN/m or more but not more than 75 mN/m.

[Surface Treatment such as Hydrophilication]

The hydrophilication of the film face of the invention can be carriedout by a publicly known method. For example, the film face can bemodified by corona discharge treatment, glow discharge treatment,ultraviolet irradiation treatment, flame treatment and acid- oralkali-treatment. The glow discharge treatment as used herein may beeither low-temperature plasma treatment under a low gas pressure of 10⁻³to 20 Torr (0.133 to 2660 Pa) or plasma treatment under atmosphericpressure. Examples of a plasma excitation gas, which is a gas plasmaexcited under the above conditions, include argon, helium, neon,krypton, xenon, nitrogen, carbon dioxide, chlorofluorocarbons such astetrafluoromethane and mixtures thereof. These gases which are describedin detail in Japan Institute of Invention and Innovation Journal ofTechnical Disclosure No. 2001-1745 (2001.03.15, Japan Institute ofInvention and Innovation), p. 30 to 32 are preferably usable in theinvention.

[Alkali Saponification Treatment]

Among these methods, alkali saponification treatment is especiallypreferred and highly effective for the surface treatment of thecellulose acylate film. The treatment can be carried out by thefollowing methods.

(1) Dipping Method

This method comprises dipping a film in an alkali solution underappropriate conditions to thereby saponify all of the faces in theentire film surface reactive with the alkali. Because of needing nospecial apparatus, this method is preferable from the viewpoint of cost.As the alkali solution, an aqueous sodium hydroxide solution may bepreferably employed. The concentration thereof preferably ranges from0.5 to 3 mol/l, especially preferably from 1 to 2 mol/l. The alkalisolution temperature is preferably from 25 to 70° C., especiallypreferably from 30 to 60° C.

After dipping in the alkali solution, it is preferable to sufficientlywash the film with water or neutralize the alkali component by dippingthe film in a dilute acid so that no alkali component remains in thefilm.

Due to the saponifying treatment, both film faces become hydrophilic.The polarizing plate-protecting film is used in such a manner that thehydrophilicated face is in contact with the polarization film.

The hydrophilicated face is effective in improving the adhesiveness tothe polarization film comprising polyvinyl alcohol as the maincomponent.

In the case where the protective film has an antireflection layer, onthe other hand, the main face thereof is also damaged by the alkali. Itis therefore important to employ the necessary and minimum conditionsfor the reaction. When the contact angle to water of the main face inthe opposite side of the support is employed as an indication of thedamage of the antireflection layer by the alkali, it preferably rangesfrom 20° to 50°, more preferably from 30° to 50° and more preferablyfrom 40° to 50° particularly in the case where the support is cellulosetriacetate. So long as it falls within this range, favorableadhesiveness to the polarization film can be maintained withoutpractically damaging the antireflection film.

(2) Coating Method with Alkali Solution

For preventing the antireflection film from being damaged in theabove-mentioned dipping method, preferably used is a method of coatingthe film with an alkali solution by applying an alkali solution to themain surface alone of the polymer film opposite to the main surfacethereof having an antireflection film thereon, then heating it, washingit with water and drying it. The details of the alkali solution and thetreatment with it are described in JP-A 2002-82226 and pamphlet ofLaid-Open No. 2002/46809. However, the method requires additionalequipment and step for coating the film with alkali solution, and istherefore inferior to the above-mentioned dipping method (1) in point ofits cost.

[Plasma Treatment]

The plasma treatment employable in the invention includes vacuum glowdischarge treatment and atmospheric pressure glow discharge treatment,as well as flame plasma treatment. These are described, for example, inJP-A 6-123062, 11-293011 and 11-5857, which are applicable to theinvention.

According to the plasma treatment, the surface of a plastic film istreated in plasma and thus the treated surface can be highlyhydrophilicated. For example, in a glow-discharge plasma generationdevice, the film to be hydrophilicated is put between a pair of facingelectrodes, and a plasma-excitable vapor is introduced into the device.Then, a high-frequency voltage is applied to the electrodes, whereby thevapor is excited by the generated plasma and glow discharge is effectedbetween the electrodes for attaining the intended surface treatment. Inparticular, atmospheric glow discharge treatment is preferred.

[Corona Discharge Treatment]

For the surface treatment, corona discharge treatment is the mostpopular method, and it may be attained by any known method, for example,as in JP-B 48-5043 and 47-51905, JP-A 47-28067, 49-83767, 51-41770 and51-131576. The corona generator for use in the corona treatment may beany commercially-available corona processor generally employed in thecurrent art for surface modification of plastic films. In particular, acorona processor equipped with multi-knife electrodes by Softalcomprises a large number of electrodes and is so designed that air isfed between the electrodes. This is effective for preventing overheatingof films and for removing low-molecular substances that may deposit onfilms, and therefore its energy efficiency is extremely high and itenables high-efficiency corona treatment. Accordingly, the coronaprocessor of the type is especially useful in the invention.

When the polymer film of the invention is used as a protective film forpolarizing plates, then the surface energy of at least one surface ofthe polymer film must be controlled to fall with a suitable range. Forthis, the above-mentioned surface treatment of the film is effected. Onthe other hand, when the polymer film of the invention is subjected tosuch surface treatment, then there may be a possibility ofvaporization/dissolution/decomposition of the additives in the polymerfilm, whereby the optical characteristics and the film properties of thepolymer film as well as the durability thereof may worsen or lower. Inthe case where the additives vaporize or dissolve, then they maycontaminate the processing system and may therefore lower theworkability of the system, and, after all, continuous treatment would beimpossible. Accordingly, the reduction in the amount of the additives inthe film must be inhibited. Concretely, it is desirable that the changeof the additive amount through the surface treatment is at most 0.2% ofthe overall amount of the additives, more preferably at most 0.1%, evenmore preferably at most 0.01%.

[Use (Optically-Compensatory Film)]

The polymer film of the invention has many applications. When it is usedfor an optically-compensatory film in liquid-crystal display devices, itis especially effective. An optically-compensatory film is generallyused in liquid-crystal display devices, and this is an optical memberfor compensating retardation. The optically-compensatory film has thesame meaning as that of a phase retarder and an optically-compensatorysheet. The optically-compensatory film has a property of birefringence,and it is used for the purpose of removing coloration of display panelsof liquid-crystal display devices and for improving the viewing anglecharacteristics of the devices. The polymer film of the invention has asmall optical anisotropy in such that its Re(630) and Rth(630) satisfy0≦Re≦10 nm and |Rth(630)|≦25 nm; and it has a reducedwavelength-dependent anisotropy distribution in such that|Re(400)−Re(700)|≦10 and |Rth(400)−Rth(700)|≦35. Accordingly, the filmdoes not have any superfluous anisotropy. When the film is combined withan optically-anisotropic layer having a birefringence, then it mayexhibit the optical characteristics of the optically-anisotropic layer.

Accordingly, when the polymer film of the invention is used as anoptically-compensatory film in liquid-crystal display devices, Re(630)and Rth(630) of the optically-anisotropic layer combined with it arepreferably as follows: Re(630)=0 to 200 nm; and |Rth(630)|=0 to 400 nm.Within these ranges, any and every optically-anisotropic layer may becombined with the film of the invention. Specifically, the film of theinvention may be combined with an optically-anisotropic layer of anytype required in optically-compensatory films, not limited by theoptical characteristics and the driving system of the liquid-crystalcell in the liquid-crystal display device in which the film is to beused. The optically-anisotropic layer to be combined with the film maybe formed of a composition containing a liquid-crystal compound, or maybe formed of a polymer film having a property of birefringence.

The liquid-crystal compound is preferably a discotic liquid-crystalcompound or a rod-shaped liquid-crystal compound.

(Discotic Liquid-Crystal Compound)

Examples of the discotic liquid-crystal compound usable in the inventionare described in various references (C. Destrade et al., Mol. Cryst.Liq. Cryst., Vol. 71, p. 111 (1981); Quarterly Journal of Outline ofChemistry, by the Chemical Society of Japan, No. 22, Chemistry of LiquidCrystal, Chap. 10, Sec. 2 (1994); B. Kohne et al., Angew. Chem. Soc.Chem. Comm., p. 1794 (1985); J. Zhang et al., J. Am. Chem. Soc., Vol.116, p. 2655 (1994)).

Preferably, the discotic liquid-crystal molecules are fixed as alignedin the optically-anisotropic layer in the invention, most preferablyfixed therein through polymerization. The polymerization of discoticliquid-crystal molecules is described in JP-A 8-27284. For fixingdiscotic liquid-crystal molecules through polymerization, apolymerizable group must be bonded to the disc core of each discoticliquid-crystal molecule as a substituent thereto. However, if such apolymerizable group is directly bonded to the disc core, then themolecules could hardly keep their orientation during polymerization.Accordingly, a linking group is introduced between the disc core and thepolymerizable group to be bonded thereto. Such polymerizablegroup-having discotic liquid-crystal molecules are disclosed in JP-A2001-4387.

(Rod-Shaped Liquid-Crystal Compound)

Examples of the rod-shaped liquid-crystal compound usable in theinvention are azomethines, azoxy compounds, cyanobiphenyls, cyanophenylesters, benzoates, phenyl cyclohexanecarboxylates,cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines,alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolans, andalkenylcyclohexylbenzonitriles. Not only such low-molecularliquid-crystal compounds, but also high-molecular liquid-crystalcompounds may also be usable herein.

In the optically-anisotropic layer, it is desirable that the rod-shapedliquid-crystal molecules are fixed in an aligned state, most preferablythey are fixed through polymerization. Examples of the polymerizablerod-shaped liquid-crystal compound usable in the invention are describedin Macromol. Chem., Vol. 190, p. 2255 (1989); Advanced Materials, Vol.5, p. 107 (1993); U.S. Pat. Nos. 4,683,327, 5,622,648, 5,770,107;pamphlets of International Laid-Open Nos. 95/22586, 95/24455, 97/00600,98/23580, 98/52905; JP-A 1-272551, 6-16616, 7-110469, 11-80081,2001-328973.

(Optically-Anisotropic Layer of Polymer Film)

The optically-anisotropic layer may be formed of a polymer film. Thepolymer film is formed from a polymer capable of expressing opticalanisotropy. Examples of the polymer are polyolefin (e.g., polyethylene,polypropylene and norbornene-based polymer), polycarbonate, polyarylate,polysulfone, polyvinyl alcohol, polymethacrylate, polyacrylate andcellulose ester (e.g., cellulose triacetate and cellulose diacetate).Copolymers or mixtures of these polymers may also be usable herein.

The optical anisotropy of the polymer film is preferably generated by anextension treatment such as stretching. The stretching is preferablymonoaxial stretching or biaxial stretching. Concretely, preferred ismachine-direction monoaxial stretching to be attained by utilizing theperipheral speed difference between two or more rolls; or tenterstretching to be attained by clipping both sides of a polymer film andstretching it in the width direction; or biaxial stretching comprising acombination of these. From the viewpoint of the productivity ofpolarizing plates as will be described hereinafter, tenter stretching orbiaxial stretching is preferred. If desired, two or more polymer filmsmay be used so that the overall optical characteristics of these two ormore films may satisfy the above-mentioned conditions. Preferably, thepolymer film is produced according to a solvent casting method in orderthat the birefringence unevenness of the film is reduced as much aspossible. Preferably, the thickness of the polymer film falls between 20and 500 μm, most preferably between 40 and 100 μm.

[Formation of Optically-Anisotropic Layer by Applying Polymer]

In the invention, the optically-anisotropic layer is formed by spreadinga polymer having been liquefied in a solvent on the polymer film of theinvention, drying it, and then carrying out an orientation treatment onthe layered matter thus obtained to give an optically-compensatory filmhaving desired optical characteristics imparted thereto. As themolecular orientation treatment, a stretching treatment, a shrinkingtreatment and both of them may be cited. From the viewpoints of theproductivity and easiness in controlling, the stretching treatment ispreferable. In this case, the polymer film of the invention would show alow optical anisotropy after the molecular orientation treatment and,therefore, a uniformly stretched film can be formed. Thus, the opticallycompensatory effect by the optically anisotropic layer is not affected,thereby facilitating optical design and the like.

The polymer as described above is not particularly restricted and one ormore polymers having appropriate light transmission properties may beemployed. It is preferable to use a polymer capable of forming a filmwith favorable light transmission properties, i.e., having a lighttransmittance of 75% or more, still preferably 85% or more. Consideringstable mass productivity of the film, it is preferable to use a solidpolymer showing positive birefringence and thus giving a largeretardation in the stretching direction.

Examples of the above-described solid polymer include polyamide,polyimide and polyester (see, for example, International PatentPublication No. 508048/1998), polyimide (see, for example, InternationalPatent Publication No. 2000-511296), polyether ketone, in particular,polyaryl ether ketone (JP-A-2001-49110), polyamide imide (see, forexample, JP-A-61-162512), polyester imide (see, for example,JP-A-64-38472) and so on. To form a birefringent film, use can be madeof one of these solid polymers or a mixture of two or more thereof.Although the molecular weight of the solid polymer is not particularlyrestricted, it is generally favorable from the viewpoint of, forexample, handling properties in film formation that the mass-averagemolecular weight thereof is from 2000 to 1000000, still preferably from1500 to 750000 and still preferably from 1000 to 500000.

In forming the polymer film, various additives such as a stabilizer, aplasticizer or metals may be added, if necessary. The solid polymer canbe liquefied by an appropriate method, for example, melting athermoplastic solid polymer by heating or dissolving a solid polymer ina solvent to give a solution.

The polymer spread on the polymer film (the spread layer) can be fixedby cooling the spared layer (in the former case of using the moltenliquid) or removing the solvent from the spread layer and drying (in thelatter case of using the solution). Drying can be performed byappropriately employing one or more methods from among spontaneousdrying (air-drying), thermal drying (in particular, thermal drying at 40to 200° C.), reduced-pressure drying and so on. From the viewpoints ofthe production efficiency and prevention of the occurrence of opticalanisotropy, it is favorable to employ the method of applying a polymersolution.

As the solvent as described above, use can be made of one or moremembers appropriately selected from among methylene chloride,cyclohexanone, trichloroethylene, tetrachloroethane,N-methylpyrrolidone, tetrahydrofuran, etc. Taking the viscosityappropriate for the film formation into consideration, the solution ispreferably prepared by dissolving form 2 to 100 parts by mass, morepreferably from 5 to 50 parts by mass and more preferably from 10 to 40parts by mass, of the solid polymer in 100 parts by mass of the solvent.

The liquefied polymer may be spread by using an appropriate film-formingmethod such as spin coating, roll coating, flow coating, printing, dipcoating, cast film-forming, casting such as bar coating and gravureprinting, extruding and so on. From the viewpoint of the mass productionof a film having little irregularities in thickness and orientation, itis preferable to employ a solution film-forming method such as thecasting method. It is especially preferred to layer the liquefiedpolymer dissolved in the solvent on a polymer film by the co-castingmethod and form a film. In such a case, it is favorable to use apolyimide which is prepared from an aromatic dianhydride and an aromaticpolydiamine and soluble in a solvent (International Patent PublicationNo. 511812/1996).

The production method of the invention wherein the above-describedpolymer is liquefied, spread on the polymer film and then stretched orshrunk, Rth is controlled in the course of forming the spread layer onthe polymer film while Re is controlled by molecular orientation bystretching or shrinking the laminate. Owing to this system of assigningfunctions, the desired object can be established at a lower stretchingrate compared with the existing method of simultaneously controlling Rthand Re as in, for example, the biaxial stretching method. Thus, abiaxial birefringent film having excellent Rth and Re characteristicsand optical axial accuracy can be advantageously obtained, therebybringing merits in design and production.

The molecular orientation treatment can be carried out by extendingand/or shrinking the film. Extension can be made by, for example, astretching treatment. As the stretching method, use can be made of oneor more methods appropriately selected from among biaxially stretchingmethods such as successive stretching and simultaneous stretching andmonoaxially stretching methods such as free-end stretching and fixed-endstretching. From the viewpoint of preventing the bowing phenomenon, themonoaxially stretching method is preferred.

The stretching temperature may be determined in accordance with theconventional methods. In general, use is made of a temperature close tothe glass transition temperature of the solid polymer as described, anda temperature not lower than the glass transition temperature. In orderto achieve lower retardation of the stretched film of the invention, itis preferred that the stretching temperature is close to the glasstransition temperature Tg of the polymer film, more preferablystretching is performed at a temperature not lower than Tg-20° C., morepreferably stretching is performed at a temperature not lower thanTg-10° C. and especially preferably stretching is performed at atemperature not lower than Tg.

Concerning the preferable range of the stretching rate, the stretchingrate is preferably 1.03 fold or more but not more than 2.50 fold, morepreferably 1.04 fold or more but not more than 2.20 fold and morepreferably 1.05 fold or more but not more than 1.80 fold, based on theunstretched film length. In the case where the stretching rate is lessthan 1.05 fold, the stretching rate is insufficient in forming theabove-described optically-anisotropic layer. In the case where thestretching ratio exceeds 2.50 fold, on the other hand, there ariseserious curling and large changes in optical characteristics after thedurability test on the film.

On the other hand, the shrinking treatment can be carried out by, forexample, performing the application and film-formation of the polymerfilm on the base material and then inducing shrinkage by takingadvantage of the dimensional change in the base material due to atemperature change or the like. In such a case, use may be also made ofa base material having shrinking ability such as a heat shrinkable film.It is favorable to control the shrinkage rate by using, for example, astretcher.

The birefringent film produced by the above method is appropriatelyusable as an optically-compensatory film for improving the viewing anglecharacteristics of liquid-crystal display devices. To construct thinnerliquid-crystal display devices and elevate the productivity by lesseningproduction stages, it is more preferable that the birefringent film isdirectly bonded to a polarizer as a protecting film for a polarizingplate. In this case, it is required to provide the above-describedpolarizing plate with the use of the optically-compensatory film at alower cost and a higher productivity. Namely, it is desired to constructthe polarizing plate at a higher productivity and a lower cost. Thus,the optically-compensatory film of the invention is used in the state ofbeing bonded to a polarizer in such a manner that the in-plane Reexpression direction is orthogonal to the absorption axis of thepolarizing plate. A polarizer of commonly employed constitution thatcomprises iodine and PVA is produced by monoaxial stretching and has theabsorption axis in the machine direction. In order to provide apolarizing plate having the cellulose acylate with the use of theabove-described birefringent film at a high productivity and a low cost,it is required to carry out the above-described construction stepcontinuously (i.e., roll to roll). Considering these factors (inparticular, productivity), it is preferable to produce theoptically-compensatory film with the use of the above-describedbirefringent film by laminating a spread layer comprising theabove-described polymer on the polymer film and then stretching orshrinking it so that the polymer in the spread layer is oriented in thetransverse direction and exhibits Re in the transverse direction. Byemploying the rolled optically-compensatory film thus produced as apolarizer-protecting film, a polarizing plate having an effectiveoptically-compensatory function can be produced as such (i.e., roll toroll).

The term “rolled film” as used herein means a film that has a length of1 m or longer in the machine direction and is wound at least three turnsin the machine direction. The term “roll to roll” means that such arolled film is subjected to any available treatment (for example,film-forming, lamination/bonding to another rolled film, surfacetreatment, heating/cooling or stretching/shrinking) while maintaining itin the rolled state before and after the treatment. From the viewpointsof productivity, cost and handling properties, a roll to roll treatmentis especially preferred.

Rth and Re of the birefringent film thus obtained can be controlleddepending on the type of the solid polymer, the method of forming thespread layer (for example, the method of coating the liquefied matter),the method of solidifying the spread layer (for example, dryingconditions), the thickness of the transparent film thus formed, and soon. The thickness of the transparent film is generally from 0.5 to 100μm, preferably from 1 to 50 μm and more preferably from 2 to 20 μm.

In the birefringent film thus obtained, the ratios of physicalparameters such as sound velocity, tensile modulus, storage modulus andphotoelasticity coefficient) in direction orthogonal to the travelingdirection in plane/the traveling direction fall within the scopes asspecified above.

The birefringent film thus produced may be used either as such or bondedto another film with the use of a pressure-sensitive adhesive or thelike.

To satisfy the requirement for the ratio R of the sound velocity in thetransverse direction VT to the sound velocity in the machine directionVM or the tensile modulus in the transverse direction, the tensile inthe machine direction and the ratio thereof as specified above, apolymer film is usually stretched in the transverse direction and shrunkin the machine direction in the invention. In the case of a laminatecomprising a polymer film and a spread layer, the laminate is similarlystretched in the transverse direction and shrunk in the machinedirection. The requirements as described above can be individuallyfulfilled by controlling the stretching or shrinking conditions.

(Constitution of General Liquid-Crystal Display Device)

In the case of using a polymer film as an optically-compensatory film,the transmission axis of the polarizing plate for it may be at any angleto the slow axis of the optically-compensatory film comprising thepolymer film. A liquid-crystal display device comprises a liquid-crystalcell that carries a liquid crystal between two electrode substrates, twopolarizing plates disposed on both sides of the cell, and at least oneoptically-compensatory film disposed between the liquid-crystal cell andthe polarizing plate.

The liquid-crystal layer of the liquid-crystal cell is generally formedby introducing a liquid crystal into the space formed by two substratesvia a spacer put therebetween, and sealed up in it. A transparentelectrode layer is formed on a substrate as a transparent film thatcontains a conductive substance. The liquid-crystal cell may furtherhave a gas barrier layer, a hard coat layer or an undercoat layer (foradhesion to transparent electrode layer). These layers are generallyformed on a substrate. The substrate of the liquid-crystal cellgenerally has a thickness of from 50 μm to 2 mm.

(Type of Liquid-Crystal Display Device)

The polymer film of the invention may be used for liquid-crystal cellsof various display modes. Various display modes such as TN (twistednematic), IPS (in-plane switching), FLC (ferroelectric liquid-crystal),AFLC (anti-ferroelectric liquid-crystal), OCB (optically-compensatorybent), STN (super-twisted nematic), VA (vertically aligned), ECB(electrically-controlled birefringence) and HAN (hybrid aligned nematic)modes have been proposed. Also proposed are other display modes with anyof the above-mentioned display modes aligned and divided. The polymerfilm of the invention is effective in liquid-crystal display devices ofany display mode. Further, it is also effective in any oftransmission-type, reflection-type and semitransmission-typeliquid-crystal display devices.

(TN-Mode Liquid-Crystal Display Device)

The polymer film of the invention may be used as a support of theoptically-compensatory film in TN-mode liquid-crystal cell-havingTN-mode liquid-crystal display devices. TN-mode liquid-crystal cells andTN-mode liquid-crystal display devices are well known from the past. Theoptically-compensatory film to be used in TN-mode liquid-crystal displaydevices is described in JP-A 3-9325, 6-148429, 8-50206 and 9-26572. Inaddition, it is also described in Mori et al's reports (Jpn. J. Appl.Phys., Vol. 36 (1997), p. 143; and Jpn. J. Appl. Phys., Vol. 36 (1997),p. 1068).

(STN-Mode Liquid-Crystal Display Device)

The polymer film of the invention may be used as a support of theoptically-compensatory film in STN-mode liquid-crystal cell-havingSTN-mode liquid-crystal display devices. In general, the rod-shapedliquid-crystal molecules in the liquid-crystal cell in an STN-modeliquid-crystal display device are twisted at an angle within a range offrom 90 to 360 degrees, and the product of the refractivity anisotropy(Δn) of the rod-shaped liquid-crystal molecules and the cell gap (d),And falls between 300 and 1500 nm. The optically-compensatory film to beused in STN-mode liquid-crystal display devices is described in JP-A2000-105316.

(VA-Mode Liquid-Crystal Display Device)

The polymer film of the invention is especially favorable for a supportof the optically-compensatory film in VA-mode liquid-crystal cell-havingVA-mode liquid-crystal display devices. Preferably, theoptically-compensatory film for use in VA-mode liquid-crystal displaydevices has a retardation Re(630) of from 0 to 150 nm and a retardation|Rth(630)| of from 70 to 400 nm. More preferably, the retardationRe(630) is from 20 to 70 nm. In the case where two optically-anisotropicpolymer films are used in a VA-mode liquid-crystal display device, thenthe retardation |Rth(630)| of the films preferably falls between 70 and250 nm. In the case where one optically-anisotropic polymer film is usedin a VA-mode liquid-crystal display device, then the retardation|Rth(630)| of the film preferably falls between 150 and 400 nm. TheVA-mode liquid-crystal display devices may have an orientation-dividedsystem, for example, as in JP-A 10-123576.

(IPS-Mode Liquid-Crystal Display Device, and ECB-Mode Liquid-CrystalDisplay Device)

The polymer film of the invention is also favorable for a support of theoptically-compensatory film and for a protecting film of the polarizingplate in IPS-mode or ECB-mode liquid-crystal cell-having IPS-modeliquid-crystal display devices and ECB-mode liquid-crystal displaydevices. In these modes, the liquid-crystal material is aligned nearlyin parallel to the film face in black display, and the liquid-crystalmolecules are aligned in parallel to the surface of the substrate whenno voltage is applied to the device for black display. In theseembodiments, the polarizing plate that comprises the polymer film of theinvention contributes to enlarging the viewing angle and to improvingthe image contrast. In these embodiments, the retardation value of theoptically-anisotropic layer disposed between the protecting film of thepolarizing plate and the liquid crystal cell is preferably at most 2times the value of Δn·d of the liquid-crystal layer. Also preferably,|Rth(630)| is at most 25 nm, more preferably at most 20 nm, even morepreferably at most 15 nm. Accordingly, the polymer film of the inventionis favorably used.

(OCB-Mode Liquid-Crystal Display Device, and HAN-Mode Liquid-CrystalDisplay Device)

The polymer film of the invention is also favorable for a support of theoptically-compensatory film in OCB-mode liquid-crystal cell-havingOCB-mode liquid-crystal display devices and HAN-mode liquid-crystalcell-having HAN-mode liquid-crystal display devices. Preferably, theoptically-compensatory film for use in OCB-mode liquid-crystal displaydevices and HAN-mode liquid-crystal display devices is so designed thatthe direction in which the absolute value of the retardation of the filmis the smallest does not exist both in the in-plane direction and in thenormal line direction of the optically-compensatory film. The opticalcharacteristics of the optically-compensatory film for use in OCB-modeliquid-crystal display devices and HAN-mode liquid-crystal displaydevices are determined, depending on the optical characteristics of theoptically-anisotropic layer, the optical characteristics of the supportand the positional relationship between the optically-anisotropic layerand the support. The optically-compensatory film for use in OCB-modeliquid-crystal display devices and HAN-mode liquid-crystal displaydevices is described in JP-A 9-197397. It is described also in Mori etal's reports (Jpn. J. Appl. Phys., Vol. 38 (1999), p. 2837).

(Reflection-Type Liquid-Crystal Display Device)

The polymer film of the invention is also favorably used for anoptically-compensatory film in TN-mode, STN-mode, HAN-mode or GH(guest-host)-mode reflection-type liquid-crystal display devices. Thesedisplay modes are well known from the past. TN-mode reflection-typeliquid-crystal devices are described in JP-A 10-123478, pamphlet ofInternational Laid-Open No. 98/48320, and Japanese Patent 3022477. Theoptically-compensatory film for use in reflection-type liquid-crystaldisplay devices is described in pamphlet of International Laid-Open No.00/65384.

(Other Liquid-Crystal Display Devices)

The polymer film of the invention is also favorably used as a support ofthe optical compensatory film in ASM (axially symmetric alignedmicrocell)-mode liquid-crystal cell-having ASM-mode liquid-crystaldisplay devices. The liquid-crystal cell in ASM-mode devices ischaracterized by being supported by a resin spacer capable ofcontrolling and varying the thickness of the cell. The other propertiesof the cell are the same as those of the liquid-crystal cell in TN-modedevices. ASM-mode liquid-crystal cells and ASM-mode liquid-crystaldisplay devices are described in Kume et al's report (Kume et al., SID98 Digest 1089 (1998)).

(Self Luminous Display Device)

The optically-compensatory film, the polarizing plate and so on of theinvention can also contribute to the improvement in the displayqualities in self luminous display devices. These self luminous displaydevices are not particularly restricted and examples thereof includeorganic EL, PDP and FED. By using a birefringent film with Re(630) of ¼wavelength in a flat panel display of a self luminous type, linearpolarization can be converted into circular polarization to give anantireflective filter.

In the above-described systems, the members constituting display devicessuch as a liquid crystal display device may be either integrated vialamination or separated. In constructing the display devices, it is alsopossible to provide appropriate optical elements such as a prism arraysheet, a lens array sheet, a light diffusion plate or a protectiveplate. In constructing display devices, these elements are also usablein the form of an optical member laminated on the birefringent film.

(Hard Coat Film, Antiglare Film, Antireflection Film)

The polymer film of the invention is favorably applied to hard coatfilms, antiglare films and antireflection films. For the purpose ofimproving the visibility of flat panel displays such as LCD, PDP, CRT,EL, any or all of a hard coat layer, an antiglare layer and anantireflection layer may be fitted to one or both faces of the polymerfilm of the invention. Preferred embodiments of such antiglare films andantireflection films are described in Japan Institute of Invention andInnovation Journal of Technical Disclosure No. 2001-1745 (2001.03.15,Japan Institute of Invention and Innovation), pp. 54-57, and the polymerfilm of the invention may be favorably used in these.

(Photographic Film Support)

The polymer film usable in the invention is applicable to supports ofsilver halide photographic materials. Regarding the techniques, JP-A2000-105445 has detailed descriptions of color negative films, and thepolymer film of the invention is favorably used in these. Alsopreferably, the film of the invention is applicable to supports of colorreversal silver halide photographic materials, and various materials andformulations and methods for processing them described in JP-A 11-282119are applicable to the invention.

(Transparent Substrate)

Since the polymer film of the invention has nearly zero opticalanisotropy and has good transparency, it may be substitutable for theglass substrate for liquid-crystal cells in liquid-crystal displaydevices, or that is, it may be usable as a transparent support forsealing up the driving liquid crystals in the devices.

Since the transparent substrate for sealing up liquid crystal must havea good gas-barrier property, a gas-barrier layer may be optionallyfitted to the surface of the cellulose acylate film of the invention, ifdesired. The morphology and the material of the gas-barrier layer arenot specifically defined. For example, SiO₂ may be deposited on at leastone face of the polymer film of the invention, or a polymer coatinglayer of a vinylidene chloride-based polymer or a vinyl alcohol-basedpolymer having a relatively higher gas-barrier property may be formed onthe film of the invention. These techniques may be suitably selected foruse in the invention.

When the film of the invention is used as a transparent substrate forsealing up liquid crystal, a transparent electrode may be fitted to itfor driving liquid crystal through voltage application thereto. Thetransparent electrode is not specifically defined. For example, a metalfilm or a metal oxide film may be laminated on at least one surface ofthe polymer film of the invention so as to form a transparent electrodeon it. Above all, a meal oxide film is preferred in view of thetransparency, the electroconductivity and the mechanical characteristicsof the film; and a thin film of indium oxide essentially comprising tinoxide and containing from 2 to 15% of zinc oxide is more preferred.These techniques are described in detail, for example, in JP-A2001-125079 and 2000-22760.

Example

Examples of the invention are mentioned below, to which, however, theinvention should not be limited.

<Preparation of Cellulose Acylate Solutions>

A composition described in Table 1 was put into a mixing tank, andstirred therein with stirring to dissolve the constitutive component,thereby preparing cellulose acylate solutions T-1 to T-3.

TABLE 1 Components of Cellulose Acylate Solution (unit: part by mass)Meth- Cellulose Acylate Cellulose ylene 1- Degree of Acylate Chlo- Meth-Buta- substi- Amount Solution ride anol nol tution added TPP BDP T-1 30054 11 2.86 100 7.8 3.9 (acetyl) T-2 300 54 11 2.86 100 no no (acetyl)T-3 300 54 11 2.92 100 no no (acetyl) TPP: triphenyl phosphate BDP:biphenyldiphenyl phosphate<Preparation of Additive Solutions>

A composition described in Table 2 was put into a mixing tank and heatedwith stirring to dissolve the components, thereby preparing additivesolutions U-1 to U-7.

TABLE 2 Composition Optical Anisotropy- Wavelength- Methylene loweringDispersion Chloride Methanol Agent Regulator Amount Amount Amount Amountadded added added added Additive (part by (part by Desig- (part byDesig- (part by Solution mass) mass) nation mass) nation mass) U-1 80 20no — — — U-2 80 20 A-19 50 — — U-3 80 20 A-19 68 UV-102  5 U-4 80 20A-19 83 UV-102 10 U-5 80 20 A-19 25 — — U-6 80 20 A-19 35 UV-102  5 U-780 20 A-19 50 UV-102 10<Fabrication of Cellulose Acylate Film Sample 001>

44 parts by mass of the additive solution U-1 was added to 477 parts bymass of the cellulose acylate solution T-1, and well stirred to preparea dope. The dope was cast onto a drum cooled at 0° C., through a castingslit. The film formed was peeled off from the drum, having a solventcontent of 70% by mass, and with its both sides in the transversedirection (the direction orthogonal to the casting direction) thereofbeing fixed to a pin tenter (as in FIG. 3 in JP-A 4-1009), this wasdried to have a solvent content of from 3 to 5% by mass in such a mannerthat the stretching rate in the transverse direction could be 2%. Next,the film was conveyed between rolls in a heat treatment device and wasfurther dried therein. Thus, a cellulose acylate film sample 001 havinga thickness of 80 μm was produced in a size of 100 m in the machinedirection (the casting direction)×1 m in the transverse direction.

<Fabrication of Cellulose Acylate Film Sample 101>

44 parts by mass of the additive solution U-2 was added to 455 parts bymass of the cellulose acylate solution T-2, and well stirred to preparea dope. In the same manner as that for producing the cellulose acylatefilm sample 001, the dope was formed into a cellulose acylate filmsample 101 having a thickness of 80 μm.

<Fabrication of Cellulose Acylate Film Samples 102 to 106>

Cellulose acylate film samples 102 to 106 each having a thickness ofabout 80 μm were produced in the same manner as that for producing thecellulose acylate film sample 101, for which, however, a combination ofthe cellulose acylate solution and the additive solution as in Table 3was used in place of those in the cellulose acylate film sample 101.

TABLE 3 Cellulose Cellulose Acylate Solution Additive Solution AcylateFilm Designa- Amount Added Designa- Amount Added Sample tion (part bymass) tion (part by mass) 001 T-1 477 U-1 44 101 T-2 455 U-2 44 102 T-2455 U-3 44 103 T-2 455 U-4 44 104 T-3 455 U-5 44 105 T-3 455 U-6 44 106T-3 455 U-7 44<Preparation of Cellulose Acylate Solution T-4>

The following composition was put into a mixing tank and stirred todissolve the components, thereby preparing a cellulose acylate solutionT-4.

<Composition of Cellulose acylate Solution T-4>

Cellulose acylate having a degree of acetylation of 2.94 100.0 mas. pts.Methylene chloride (first solvent) 402.0 mas. pts. Methanol (secondsolvent)  60.0 mas. pts.<Preparation of Mat Agent Solution>

20 parts by mass of silica particles having a mean particle size of 16nm (Aerosil R972 by Nippon Aerosil) and 80 parts by mass of methanolwere well stirred and mixed for 30 minutes to prepare a dispersion ofsilica particles. The dispersion was put into a disperser along with thefollowing composition thereinto, and further stirred therein for atleast 30 minutes to dissolve the components, thereby preparing a matagent solution.

(Composition of Mat Agent Solution)

Dispersion of silica particles having a mean particle 10.0 mas. pts.size of 16 nm Methylene chloride (first solvent) 76.3 mas. pts. Methanol(second solvent)  3.4 mas. pts. Cellulose acylate solution (T-6) 10.3mas. pts.<Preparation of Additive Solution U-8>

The following composition was put into a mixing tank, and heated withstirring to dissolve the components, thereby preparing an additivesolution U-8.

(Composition of Additive Solution U-8)

Compound capable of lowering optical anisotropy (A-19) 90.0 mas. pts.Wavelength-distribution regulator (UV-102)  9.0 mas. pts. Methylenechloride (first solvent) 58.4 mas. pts. Methanol (second solvent)  8.7mas. pts. Cellulose acylate solution (T-4) 12.8 mas. pts.<Fabrication of Cellulose Acylate Film Sample 107>

94.6 parts by mass of the cellulose acylate solution (T-4), 1.3 parts bymass of the mat agent solution, and 4.1 parts by mass of the additivesolution (U-8) were separately filtered, and then mixed. Using a bandcaster, the mixture was cast on a band. In the above-mentionedcomposition, the ratio by mass of the compound capable of loweringoptical anisotropy and the wavelength distribution regulator tocellulose acylate was 12% and 1.2% by mass, respectively. The filmhaving a remaining solvent content of 30% was peeled away from the band,and dried at 140° C. for 40 minutes to give a cellulose acylate filmsample 107. The remaining solvent content of the thus-produced celluloseacylate film was 0.2%, and the thickness of the film was 80 μm.

[Fabrication of Norbornene-Based Polymer Sample 301]

Fine needle crystals of calcium carbonate (Maruo Calcium Co., Ltd.) wereuniformly dispersed in THF by ultrasonic irradiation. Further Artonpellets (JSR) were added as a polymer and dissolved by stirring forabout 30 hours. Concerning the mixing ratio, tetrahydrofuran wasemployed in an amount 5 times as much as Arton, while calcium carbonatewas employed in the amount of 1.1 mass % based on Arton. The polymersolution thus obtained was spread on a glass plate with the use of aknife coater and the solvent was evaporated. Then the filmy sample(thickness: about 80 μm) was peeled off from the glass plate and driedat 82° C. for 2 hours to give a norbornene-based polymer sample 301.

<Measurement of Glass Transition Temperatures (Tg) of Film Samples>

The glass transition temperatures (Tg) of the samples thus fabricatedwere measured in accordance with the method as described in the presentspecification.

<Stretching Treatment>

The cellulose acylate sample 001 thus fabricated was stretched. Bycutting the film sample in an adequate size, the stretching treatmentwas carried out monoaxially in the transverse direction with the use ofa multipurpose testing machine Tensilon (manufactured by ORIENTEC, Co.).The stretching temperature was 150° C., the stretching speed was 15%/minagainst the film width and the stretching rate was 1.18 fold. Thus, astretched film sample 001A was obtained.

(Stretching Treatment on Samples 101 to 107 and 301)

The cellulose acylate samples 101 to 107 and 301 fabricated above weresimilarly stretched as in the sample 001 to give stretched film samples101A to 107A and 301A.

(Fabrication of Samples Changing Stretching Temperature)

The cellulose acylate samples 102 and 105 fabricated above werestretched in the same manner but at a stretching temperature of 120° C.to give stretched film samples 201A and 202A.

(Fabrication of Samples with Different Stretching Rate)

The cellulose acylate samples 102 and 105 fabricated above werestretched in the same manner but at a stretching rate of 1.55 fold togive stretched film samples 203A and 204A.

<Surface Treatment>

Next, the stretched cellulose acylate film sample 001A fabricated abovewas subjected to the following surface treatment.

The stretched cellulose acylate film sample 001A was dipped in anaqueous 1.5 N sodium hydroxide solution at 55° C. for 2 minutes. Then,it was washed in a wash water bath at room temperature, and neutralizedwith 0.1 N sulfuric acid at 30° C. Again, it was washed in a wash waterbath at room temperature, and dried with a hot air stream at 100° C. Inthat manner, the surface of the cellulose acylate film wasalkali-saponified to give a saponified film sample 001B.

(Surface Treatment on Stretched Film Samples 101A to 107A, 201A to 204Aand 301A)

The stretched film samples 101A to 107A, 201A to 204A and 301A weresurface-treated as in the stretched film sample 001A to givesurface-treated samples 101B to 107B, 201B to 204B and 301B.

<Evaluation of Optical Performance>

The surface-treated and surface-untreated film samples produced hereinwere evaluated in their optical properties of Re(630), |Rth(630)|,|Re(400)−Re(700)| and |Rth(400)−Rth(700)| in accordance with the methoddescribed in the present specification.

<Evaluation of Film Performance>

The surface-treated film samples produced herein were evaluated intensile moduli, sound velocities and photoelasticity coefficients in themachine direction and in the transverse direction in accordance with themethod described in the present specification.

<Determination of Surface Energy>

The surface energies of the surface-treated and surface-untreated filmsamples produced herein were determined as follows. Concretely, a filmsample (30 mm×40 mm) taken from the center was conditioned at 25° C. and60% RH for 2 hours and then put on a horizontal bed horizontally. Next,a predetermined amount (20 μl) of water and methylene iodide wereapplied onto the surface of the sample. After a predetermined period oftime (30 seconds), the contact angle of the sample surface with waterand with methylene iodide was measured. From the data of thethus-measured contact angle, the surface energy (surface E) of thesample was derived according to an Owens method.

<Evaluation of Durability of Polarizing Plate>

[Lamination Test of Polarizing Plate]

The polarizing plate described below was fabricated usingsurface-treated and surface-untreated film samples described above.Namely, a rolled polyvinyl alcohol film having a thickness of 80 μm wascontinuously stretched 5-fold in an aqueous iodine solution, and driedto obtain a polarizing film. The surface treated film sample 001B and asurface treated commercially available cellulose acylate film (FujitakTD80UF, FUJI PHOTOFILM Co., Ltd.; Re(630) 3 nm, |Rth(630)|50 nm), whichhad been surface-treated in the same manner as in sample 001B, werebonded to the polarization film with its surface (surface-treatedsurface) towards the polarization film side as sandwiching thepolarization film located therebetween from both side by using polyvinylalcohol based pressure-sensitive adhesives, thereby giving a polarizingplate sample 001C, which both sides were protected with the celluloseacetate film 001B and the commercially available cellulose acylate film(Fujitak TD80UF, FUJI PHOTOFILM Co., Ltd.).

The surface-treated samples 101B to 107B, 201B to 204B and 301B weretreated in the same manner to thereby give polarizing plate samples 101Cto 107C, 201C to 204C. Similarly, the surface-untreated samples 001A,101A to 107A, 201A to 204A and 301A were treated in the same manner tothereby give polarizing plate samples 001D, 101D to 107D, 201D to 204Dand 301D.

(Adhesiveness)

The thus-fabricated polarizing plate samples were tested for theiradhesiveness, according to the method mentioned below. Concretely, eachpolarizing plate sample was folded at 90 degrees repeatedly for fivetimes all at a predetermined site thereof, and the adhesiveness of eachsample was evaluated in point of the presence or absence of delaminationof the folded part of the sample.

A: No delamination found.

B: Delamination found.

(Workability)

The polarizing plate samples fabricated herein were tested for theirworkability, according to the method mentioned below. Concretely, thepolarizing plate sample was cut with a single-edged cutter knife, andits workability was evaluated in point of the presence or absence ofdelamination around the cut part of the sample.

A: No delamination found.

B: Delamination found.

(Adhesiveness Durability 1)

The polarizing plate samples fabricated herein were tested for theiradhesiveness durability, according to the method mentioned below.Concretely, the polarizing plate sample was kept under a condition of60° C./90% RH for 200 hours, and then its adhesiveness durability wasevaluated in point of the presence or absence of delamination of thesample after stored.

<Delamination>

A: No delamination found.

B: Delamination found.

<Adhesiveness Durability 2>

The polarizing plate samples fabricated herein were tested for theiradhesiveness durability, according to the method mentioned below.Concretely, the polarizing plate sample was kept at 80° C. for 200hours, and then its adhesiveness durability was evaluated in point ofthe presence or absence of delamination of the sample after stored.

<Delamination>

A: No delamination found.

B: Delamination found.

Tables 4 to 6 show the evaluation data of the fabricated samples. InTable 4, Re(20 stands for Re(630), Rth(λ) stands for |Rth(630)|, ΔRe(2)stands for |Re(400)−Re(700)| and ΔRth(λ) stands for 1Rth(400)−Rth(700)|.

TABLE 4 Film (unsaponified sample: indicated in A) PhotoelasticityOptical performance Sound velocity ratio Tensile modulus coefficient ReRth ΔRth ΔRe R R R (λ) (λ) (λ) (λ) Tg TD MD TD/MD TD MD TD/MD TD MDTD/MD Remark Film Unit Sample nm nm nm nm ° C. kgf/mm² GPa kgf/mm² GPa×10⁻¹³M/m² Comp. 001A 1 42 27 2 180 2.41 2.20 1.10 455 4.46 375 3.681.21 14.3 15.8 0.91 Ex. 101A 2 1 20 1 146 2.43 2.22 1.09 475 4.66 3893.81 1.22 12.2 13.2 0.92 Ex. 102A 1 0 14 1 132 2.40 2.19 1.10 480 4.70395 3.87 1.22 12.1 12.9 0.94 Ex. 103A 1 0 8 2 122 2.39 2.20 1.09 4694.60 387 3.79 1.21 12.0 12.9 0.93 Ex. 104A 1 1 20 1 161 2.44 2.21 1.10473 4.64 390 3.82 1.21 11.8 12.9 0.91 Ex. 105A 1 0 13 1 153 2.46 2.221.11 461 4.52 385 3.77 1.20 11.7 12.5 0.94 Ex. 106A 1 0 7 2 141 2.442.21 1.10 453 4.44 377 3.69 1.20 11.4 12.2 0.93 Ex. 107A 1 0 13 1 1542.43 2.21 1.10 463 4.54 384 3.76 1.21 11.5 12.3 0.93 Ex. 201A 1 8 15 2132 2.39 2.20 1.09 475 4.66 393 3.85 1.21 12.3 13.1 0.94 Ex. 202A 1 7 142 153 2.44 2.21 1.10 464 4.55 378 3.70 1.23 11.9 12.6 0.94 Ex. 203A 5 1217 1 132 2.75 2.13 1.29 533 5.22 379 3.71 1.41 11.7 13.4 0.87 Ex. 204A 411 16 1 153 2.71 2.11 1.28 541 5.30 386 3.78 1.40 11.5 13.8 0.83 Ex.301A 24 45 2 0 148 2.01 1.81 1.11 298 2.92 245 2.40 1.22 2.0 3.0 0.67Comp.

TABLE 5 Unsaponified sample (indicated in A) Saponified sample(indicated in B) Surface energy (unsaponified) Surface energy(saponified) Methylene Methylene Surface E H₂O iodide Surface E H₂Oiodide Film Unit Sample mN/m ° ° mN/m ° ° Remark 001 46 73 28 62 37 33Comp. 101 47 75 27 66 30 32 Ex. 102 47 73 27 62 39 31 Ex. 103 47 73 2762 39 31 Ex. 104 46 75 28 62 39 32 Ex. 105 47 75 27 64 35 32 Ex. 106 4774 27 63 33 32 Ex. 107 47 75 27 64 35 32 Ex. 201 46 75 28 62 38 31 Ex.202 47 74 27 63 34 32 Ex. 203 46 75 27 62 39 31 Ex. 204 47 76 27 64 3632 Ex. 301 40 96 40 39 91 42 Comp.

TABLE 6 Polarizing plate Unsaponified polarizing plate (indicated in D)Saponified polarizing plate (indicated in C) Having polarizing plateDurability 1 Durability 2 Having polarizing plate Durability 1Durability 2 Adhesive- Work- Delami- Delami- Adhesive- Work- Delami-Delami- Sample ness ability nation nation ness ability nation nationRemark 001 B B B B A A A A Comp. 101 B B B B A A A A Ex. 102 B B B B A AA A Ex. 103 B B B B A A A A Ex. 104 B B B B A A A A Ex. 105 B B B B A AA A Ex. 106 B B B B A A A A Ex. 107 B B B B A A A A Ex. 201 B B B B A AA A Ex. 202 B B B B A A A A Ex. 203 B B B B A A A A Ex. 204 B B B B A AA A Ex. 301 B B B B B B B B Comp.(Formation of Optically-Anisotropic Layer)<Direct Stretching Method>

On the cellulose acetate film sample 001 obtained above, a 17% by masscyclohexanone solution of polyimide (mass-average molecular weight (Mw):60000) synthesized from 2,2′-bis(3,4-dicarboxyphenyl)hexafluoropropanewith 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl was applied. Afterdrying at 95° C. for 12 minutes, a transparent film containing 6% bymass of the remaining solvent, having a thickness of 6 μm, |Rth(630)| of233 nm and Re(630) of 0 was obtained. In the state of laminated on thefilm sample 001, the obtained polymer film was monoaxially stretched inthe transverse direction at the glass transition temperature (Tg)-5° C.to give an optically-compensatory film 001E having Re(630) of 55 nm and|Rth(630)| of 238 nm and showing optical anisotropy.

(Fabrication of Samples 101E to 107E and 301E)

The cellulose acylate film samples 101 to 107 and 301 were treated inthe same manner to give optically-compensatory film samples 101E to 107Eand 301E.

(Fabrication of Samples 201E and 202E)

The cellulose acylate film samples 102 and 105 were treated in the samemanner as in the direct stretching method described above but at astretching temperature of 120° C. to thereby give optically-compensatoryfilm samples 201E and 202E.

(Fabrication of Samples 203E and 204E)

The cellulose acylate film samples 102 and 105 were treated in the samemanner as in the direct stretching method described above butsubstituting the polymer employed by a polyimide of the followingformula PI-1 (weight average molecular weight (Mw): 50000) and at astretching rate of 1.60 to thereby give optically-compensatory filmsamples 203E and 204E.

<Alkali-Saponification Treatment>

The optically-compensatory film sample 001E was alkali-saponified asdescribed above to give a surface-treated sample 001F.

(Fabrication of Samples 101F to 107F, 201F to 204F and 301F)

The optically-compensatory film samples 101E to 107E, 201E to 204E and301E were treated in the same manner to thereby give surface-treatedsamples 101F to 107F, 201F to 204F and 301F.

(Fabrication of Polarizing Plate)

Using the surface-treated samples 001F, 101F to 107F, 201F to 204F and301F, polarizing plate samples 001G, 101G to 107G, 201G to 204G and 301Gwere fabricated as in the fabrication of the polarizing plate sample001C. Concerning the bonding faces of each surface-treated sample, anadhesive layer was provided on the cellulose acylate film face of thesurface-treated film in the side having no optically-anisotropic layerand the face having the adhesive layer was bonded to a polarizationfilm. Further, a commercially available cellulose acylate film (FujitakTD80UF, FUJI PHOTOFILM Co., Ltd.; Re(630) 3 nm, |Rth(630)|50 nm), whichhad been alkali-saponified in the same manner as described above, wasbonded to the other side of the polarization film via an adhesive layer,thereby giving a polarizing plate sample C.

Further, two sheets of a commercially available cellulose acylate film(Fujitak TD80UF, FUJI PHOTOFILM Co., Ltd.; Re 3 nm, Rth 50 nm), whichhad been alkali-saponified in the same manner as described above and onwhich adhesive layers had been formed, were bonded in both sides of thepolarization film to thereby give a polarizing plate sample 301B.

<Polarizing Plate Evaluation>

The polarizing plate samples 001G, 101G to 107G, 201G to 204G and 301Gwere evaluated in adhesiveness, workability and adhesiveness durabilityeach in the same manner as described above.

(Evaluation of Mounting on VA Type Liquid Crystal Display Device)

<Construction of Perpendicularly Oriented Liquid Crystal Cell>

To a 3% by mass aqueous solution of polyvinyl alcohol, 1% by mass ofoctadecyldimethylammonium chloride (a coupling agent) was added. Themixture was spin-coated on a glass substrate provided with an ITOelectrode and heated at 160° C. Next, it was rubbed to give aperpendicularly oriented film. The rubbing treatment was carried out inopposite directions to each other on two glass substrates. The glasssubstrates were faced to each other to give a cell gap (d) of about 4.3μm. A liquid crystal compound mainly comprising an ester and ethane(Δn:0.06) was injected into the cell gap to give a perpendicularlyorientated liquid crystal cell. The product Δnd was 260 nm. To thisliquid crystal cell, the above-described polarizing plate sample 001Gwas bonded with a pressure-sensitive adhesive in such a manner that theoptically-anisotropic layer was located in the liquid crystal cell side.Further, the polarizing plate 301B was bonded to the other side of theliquid crystal cell with a pressure-sensitive adhesive so that theopposite polarizing plate and the absorption axis were at right anglesto one another. Thus, a VA type liquid crystal display device wasconstructed.

Separately, VA type liquid crystal display devices were fabricated inthe same manner but using the polarizing plate samples 101G to 107G,201G to 204G and 301G.

<Evaluation Test>

[Panel Evaluation]

<Evaluation of Optically-Compensatory Films and Measurement of LightLeakage of Liquid Crystal Display Devices>

The viewing angle dependency of each of the liquid crystal displaydevices thus constructed was measured. The elevation angles weremeasured up to 80° at intervals of 10° from the front face directiontoward an oblique direction. Azimuthal angles were measured up to 360°C. at intervals of 10° by using the horizontal direction (0°) as thestandard. Thus, it was clarified that light leakage in the luminance inblack display increased with an increase in the elevation angle from thefront face direction and attained the maximum level at around theelevation angle 70°. It was also found out that contrast was worsenedwith an increase in the black display transmittance. Thus, the viewingangle characteristics were evaluated based on the black displaytransmittance in the front face direction and the maximal light leakagein the range of 0 to 360° at the elevation angle of 60°.

In a durability test, display light leakages were observed aftertreating at 60° C. and 90% RH for 150 hours. Light leakages occurredmainly in the four corners of the panel.

Table 7 summarizes the obtained results.

TABLE 7 Having optically-anisotropic layer (indicated in G) Polar-Bonding polarizing plate Durability 1 Durability 2 Panel evaluation izerAdhesive- Work- Delami- Delami- Contrast Color Irregu- Sample nessability nation nation change change ralities Remark 001G B B B B D D CComp. 101G B B B B A B A Ex. 102G B B B B A A A Ex. 103G B B B B A A AEx. 104G B B B B A B A Ex. 105G B B B B A A A Ex. 106G B B B B A A A Ex.107G B B B B A A A Ex. 201G B B B B B B A Ex. 202G B B B B B B A Ex.203G B B B B B B A Ex. 204G B B B B B B A Ex. 301G D D D D D D C Comp.

From the results in Table 7, it can be understood that the inventionsamples had favorable viewing angle characteristics of liquid crystaldisplay and showed little irregularities on panels.

<Evaluation of Changes in Display Characteristics>

<Change in Viewing Angle Contrast>

A: Excellent with little difference in viewing angle characteristics.

B: Good with a slight difference in viewing angle characteristics.

C: A slight difference in viewing angle characteristics.

D: A large difference in viewing angle characteristics.

<Evaluation of Viewing Angle-Dependent Color Change>

A: Excellent with little difference in viewing angle dependent colorchange.

B: Good with a slight difference in viewing angle dependent colorchange.

C: A slight difference in viewing angle-dependent color change.

D: A large difference in viewing angle-dependent color change.

<Evaluation of Display Irregularities>

A: Good with slight irregularities.

B: Slight irregularities.

C: Serious irregularities.

According to the invention, it is found that a polymer film showingsmall retardation after a stretching treatment and having a highdurability in the case of employed as a protecting film for polarizingplates can be obtained. It is also found that, by using the polymer filmof the invention as a support and providing an optically-anisotropiclayer thereon by coating and stretching, it is possible to provide aproduct that is excellent in viewing angle characteristics anddurability as an optically-compensatory film for panels inliquid-crystal display devices, etc.

INDUSTRIAL APPLICABILITY

According to the invention, it is possible to provide a polymer filmwhich has a low optical anisotropy (i.e., being substantially opticallyisotropic), even optical characteristics without irregularities(preferably having a small wavelength dispersion in the opticalanisotropy) and controlled bonding properties so that it isappropriately usable in image display devices such as liquid-crystaldisplay devices.

According to the invention, it is also possible to provide anoptically-compensatory film using the above polymer film, a process forproducing the same, a polarizing plate having excellent viewing anglecharacteristics and a liquid-crystal display device using the abovepolarizing plate.

The entire disclosure of each and every foreign patent application fromwhich the benefit of foreign priority has been claimed in the presentapplication is incorporated herein by reference, as if fully set forth.

The invention claimed is:
 1. A polymer film comprising a celluloseacylate which is a protecting film for a polarizing plate and that has:a ratio R (VT/VM) of a sound velocity in a transverse direction VT to asound velocity in a machine direction VM of from 1.05 to 1.50; a tensilemodulus in a transverse direction of from 453 to 600 kgf/mm² (4.44 GPato 5.88 GPa), a tensile modulus in the machine direction of from 230 to480 kgf/mm² (2.25 GPa to 4.70 GPa); a ratio of a tensile modulus in atransverse direction to a tensile modulus in a machine direction of from1.15 to 1.22; an in-plane retardation Re(λ) and a thickness-directionretardation Rth(λ) satisfying formula (I):0≦Re(630)≦10, and |Rth(630)|≦25  (I) wherein Re(λ) represents anin-plane retardation at a wavelength of λ (nm); and Rth(λ) represents athickness-direction retardation at a wavelength of λ (nm); and anin-plane retardation Re(λ) and a thickness-direction retardation Rth(λ)satisfying formula (II):|Re(400)−Re(700)|≦10, and |Rth(400)−Rth(700)|≦14;  (II) wherein Re(λ)represents an in-plane retardation at a wavelength of λ (nm); and Rth(λ)represents a thickness-direction retardation at a wavelength of λ (nm),and wherein an acyl substituent in the cellulose acylate issubstantially an acetyl group alone, and a total degree of substitutionthereof is from 2.80 to 2.99.
 2. The polymer film according to claim 1,which has a slow axis in a direction close to the machine direction orclose to the transverse direction.
 3. The polymer film according toclaim 2, which has at least one surface-treated surface, wherein the atleast one surface-treated surface has a surface energy of 30 mN/m ormore but not more than 50 mN/m before a surface treatment, and has asurface energy of 50 mN/m or more but not more than 80 mN/m after asurface treatment.
 4. The polymer film according to claim 1, which hasat least one surface having a surface energy of 50 mN/m or more but notmore than 80 mN/m.
 5. The polymer film according to claim 1, which is apolymer film comprising at least a cellulose acylate and a compoundhaving a molecular weight of not more than
 3000. 6. The polymer filmaccording to claim 1, which has a photoelasticity coefficient of notmore than 25×10⁻¹³ cm²/dne (2.5×10⁻¹³ N/m²).
 7. A polarizing platecomprising a polymer film according to claim 1 as a protecting film fora polarization film.
 8. The polarizing plate according to claim 7, whichhas at least one layer selected from the group consisting of a hard coatlayer, an antiglare layer and an antireflection layer provided on asurface of the polarizing plate.
 9. The polarizing plate according toclaim 7, which has an absorption axis in the machine direction.
 10. Aliquid-crystal display device, which comprises a polymer film accordingto claim
 1. 11. The liquid-crystal display device according to claim 10,which is a VA or IPS liquid-crystal display device.
 12. The polymer filmaccording to claim 1, which has a ΔRth(400)=Rth(400)10% RH−Rth(400)80%RH) that ranges from 0 to 50 nm.
 13. The polymer film according to claim1, which has a ΔRe(400)=Re(400)10% RH−Re(400)80% RH) that ranges from 0to 10 nm.
 14. The polymer film according claim 1, wherein the polymerfilm is a rolled film.
 15. A polymer film comprising a cellulose acylateand mat agent particles which is a protecting film for a polarizingplate and that has: a ratio R (VT/VM) of a sound velocity in atransverse direction VT to a sound velocity in a machine direction VM offrom 1.05 to 1.50; a tensile modulus in a transverse direction of from453 to 600 kgf/mm² (4.44 GPa to 5.88 GPa), a tensile modulus in themachine direction of from 230 to 480 kgf/mm² (2.25 GPa to 4.70 GPa); aratio of a tensile modulus in a transverse direction to a tensilemodulus in a machine direction of from 1.15 to 1.22; an in-planeretardation Re(λ) and a thickness-direction retardation Rth(λ)satisfying formula (I):0≦Re(630)≦10, and |Rth(630)|≦25  (I) wherein Re(λ) represents anin-plane retardation at a wavelength of λ (nm); and Rth(λ) represents athickness-direction retardation at a wavelength of λ (nm); and anin-plane retardation Re(λ) and a thickness-direction retardation Rth(λ)satisfying formula (II):|Re(400)−Re(700)|≦10, and |Rth(400)−Rth(700)|≦14;  (II) wherein Re(λ)represents an in-plane retardation at a wavelength of λ (nm); and Rth(λ)represents a thickness-direction retardation at a wavelength of λ (nm);and wherein an acyl substituent in the cellulose acylate issubstantially an acetyl group alone, and a total degree of substitutionthereof is from 2.80 to 2.99.
 16. The polymer film according to claim15, which has a slow axis in a direction close to the machine directionor close to the transverse direction.
 17. A polarizing plate comprisinga polymer film according to claim 15 as a protecting film for apolarization film.
 18. A liquid-crystal display device, which comprisesa polymer film according to claim
 15. 19. The polymer film accordingclaim 15, wherein the polymer film is a rolled film.